A medical condition caused or aggravated by hazards of a particular job or work environment.

"Occupational" limits the condition to risks connected to the employment, not everyday exposure faced equally by the general public. "Disease" includes illnesses that develop over time, such as lung damage, hearing loss, repetitive-stress conditions, or chemical-related disorders, rather than only a single traumatic event. "Caused or aggravated" matters because work does not always have to be the sole cause; a claim may still qualify if job exposures materially worsened a preexisting condition. The key issue is causation: whether the worker's duties, substances, motions, noise, or environment medically produced the illness.

For a South Dakota workers' compensation claim, occupational disease issues are governed primarily by SDCL chapter 62-8. South Dakota generally requires proof that the disease arose out of and in the course of employment and is not merely an ordinary disease of life to which the public is equally exposed outside the job, unless the employment created the risk in a greater degree. Medical records, exposure history, job duties, and expert opinion usually decide the dispute.

The term matters because these claims are often contested more heavily than obvious accident injuries. An insurer may dispute whether the condition came from work, from aging, smoking, hobbies, or prior health problems. That can affect compensability, temporary disability benefits, medical treatment, and any later permanent impairment award.