Incidence rates and characterizations of occupational carbon monoxide (CO) poisoning in terms of sources of exposures, diagnosis, treatment, and health care utilization are critical for public health planning. We identified 182 CO poisoning cases occurring over a 6-year period (IR = 4.3/100, 000 worker-years) in the West Virginia workers' compensation data. Frequent sources Of poisoning were gas-powered engines (28%) and furnaces (20%). Minimum treatment duration ranged from I day to 8 years with significant differences in mental health comorbidities between cases treated within I year compared with cases treated for more than 1 year (OR = 20.75; 95% CI = 3.5-128.4). The average cost (medical and wage loss replacement)for CO claims was $2130 and median lost time was 45 days. CO poisoning could lead to prolonged disability and treatment in patients with mental health comorbidities, suggesting a possible role for early intervention.