The Occupational Injury and Illness Classification System (OIICS) was developed by the Bureau of Labor Statistics (BLS) to provide a standardized coding system for characterizing work-related injuries and illnesses. The OIICS has four component hierarchical coding structures or “code trees.” Each structure is used to characterize specific incident concepts (referred to here as coding components). Two coding structures are used to describe the characteristics of the injury or illness (i.e., "Nature" and "Part of Body Affected") and two structures are used to describe the incident circumstances (i.e., "Source/Secondary Source of injury or illness", and "Event or Exposure"). The Source and Secondary Source coding components utilize the same hierarchical coding structure. However, the coding rules differ slightly. Thus, the four coding structures represent five data elements or conceptual components.

Each coding component is represented by a hierarchical coding structure with up to four levels of detail represented by numeric codes with 1-4 digits. At the highest level of the coding structure are division titles (1 digit) followed by levels with successively more detailed descriptors: major groups (2 digit), groups (3 digit) and finally the fourth level which provides the most specificity for each component in the hierarchical coding structure (4 digit). Category “titles” occur at division, major group, and group levels and are indicated by a numeric code followed by an asterisk (e.g., for Source of injury or illness: 4* PARTS AND MATERIALS, 41* Building materials—solid elements, and 411* Bricks, blocks, structural stone). Codes followed by an asterisk denote a summary-level code not assigned to individual cases. In the example sequence, an individual case would be assigned one of the 4-digit Source codes: 4110 Bricks, blocks, structural stone, unspecified; 4111 Bricks and pavers; 4112 Concrete blocks, cinder blocks; 4113 Stone, marble, granite slabs; 4114 Structural stones or slabs, n.e.c.; or 4119 Bricks, blocks, structural stone, n.e.c. (n.e.c. = not elsewhere classified).

Two subclasses within each of the second through fourth levels are used to classify characteristics that cannot be classified with more specificity (i.e., characteristics that are unspecified; e.g., 4110 Bricks, blocks, structural stone, unspecified) and characteristics that cannot be specifically fit into one of the subclasses (i.e., characteristics that are not elsewhere classified; e.g., 4119 Bricks, blocks, structural stone, n.e.c.). When a group does not lend itself to further subclasses at the third or fourth levels the hierarchical scheme is truncated.

Individual worker injury and illness incidents are coded to two to four digits, depending upon the OIICS component and the amount of information available with which to classify the case. For analysis purposes, similar cases may be grouped at any of the four levels from division titles to the most detailed 4-digit classifications.

Specific coding selection rules are used for each OIICS coding component. Code descriptions and informational notes are provided at numerous levels within each coding structure. The selection rules and informational material are embedded in the graphical tree interfaces provided here as well as in the OIICS manuals. The OIICS manuals also include alphabetical indices for each coding component.

OIICS Division Titles (v2.01)
Nature of Injury or Illness Part of Body Affected Source & Secondary Source Event or Exposure
1* Traumatic Injuries and Disorders
2* Systemic Diseases or Disorders
3* Infectious and Parasitic Diseases
4* Neoplasms, Tumors, and Cancer
5* Symptoms, Signs, and Ill-defined Conditions
6* Other Diseases, Conditions, and Disorders
7* Exposures to Disease—No Illness Incurred
8* Multiple Diseases, Conditions, or Disorders
9999 Nonclassifiable
1* Head
2* Neck, Including Throat
3* Trunk
4* Upper Extremities
5* Lower Extremities
6* Body Systems
8* Multiple Body Parts
9* Other Body Parts
9999 Nonclassifiable
1* Chemicals and Chemical Products
2* Containers, Furniture, and Fixtures
3* Machinery
4* Parts and Materials
5* Persons, Plants, Animals, and Minerals
6* Structures and Surfaces
7* Tools, Instruments, and Equipment
8* Vehicles
9* Other Sources
9999 Nonclassifiable
1* Violence and Other Injuries by Persons or Animals
2* Transportation Incidents
3* Fires and Explosions
4* Falls, Slips, Trips
5* Exposure to Harmful Substances or Environments
6* Contact with Objects and Equipment
7* Overexertion and Bodily Reaction
9999 Nonclassifiable

The BLS uses the OIICS to characterize occupational fatalities collected through their Census of Fatal Occupational Injuries (CFOI)and nonfatal injuries and illnesses collected through their annual survey of employers, the Survey of Occupational Injuries and Illnesses (SOII).The American National Standards Institute (ANSI) adopted the OIICS as the basis for the ANSI Z16.2-1995 American National Standard for Information Management for Occupational Safety and Health. NIOSH uses the OIICS to characterize nonfatal occupational injuries and illnesses treated in emergency departments (Work-RISQS).

Initially, the BLS used the OIICS 1992 version 1 and subsequently the slightly revised 2007 OIICS version (v1.01) to characterize fatal and nonfatal occupational injuries and illnesses that occurred up through 2010. Beginning with fatal and nonfatal data for 2011, the BLS used OIICS version 2.01 for classification purposes. Although there are significant conceptual and structural similarities between versions 1 and 2, the OIICS “comprehensive redesign” resulted in a break in series for BLS data beginning with injuries and illnesses occurring in 2011. To aid researchers and others in using data coded OIICS version 1, this website includes the online hierarchical trees and the downloadable software tool for OIICS v1.01.

Data Source

U.S. Department of Labor, Bureau of Labor Statistics, 2012. Available at Occupational Injury and Illness Classification System Manual.


The coding structures are subject to change without notice. NIOSH makes no warranties or representations regarding the accuracy or completeness of the OIICS information contained in this site. In no event shall NIOSH or the BLS be liable for any incidental or consequential damages, lost profits or data, or any indirect damages even if NIOSH or BLS has been informed of the possibility thereof. The use of product or trade names herein does not imply endorsement of the U.S. Government.

Page last reviewed: December 9, 2023
Content source: National Institute for Occupational Safety and Health (NIOSH) Division of Safety Research