OBJECTIVES: To describe demographics of opioid abusers, and compare medical/drug utilization, workloss patterns, and medical costs of opioid abusers to those of a control group, 1999-2002 METHODS: A claims database of insured patients was used to identify patients with claims with ICD-9 codes for opioid abuse (304.0, 304.7, 305.5, and 965.0). In total, 740 such patients aged 12-64 were identified. A control group of non-abusers was selected using a matched sample (by age, gender, and census region). All costs were calculated from a private payer's perspective in 2003USD. RESULTS: Opioid abusers, compared to controls, had higher medical and drug utilization. Almost 60% of opioid abusers had claims for opioids, versus 20% for controls. Prevalence rates for hospital inpatient care for opioid abusers were 12 times higher than controls (p<0.01). Opioid abusers were 1.5-fold as likely to have medically related absenteeism days, and 8.5 times as likely to have a disability claim compared to controls (p<0.01). Opioid abusers had higher average annual medically related absenteeism days compared to controls (26.4 days vs. 5.7 days, p<0.01). Mean annual direct health care costs for opioid abusers were over eight times higher than controls ($15,884 vs. $1,830, p<0.01). Hospital inpatient and doctor/outpatient costs accounted for 46% ($7239) and 31% ($5000) of opioid abusers' health care costs, versus 17% ($310) and 50% ($906), respectively, for controls. Mean annual indirect workloss costs for opioid abusers were over eight times higher than controls ($4167 vs. $502, p<0.01). CONCLUSIONS: These high costs were driven partly by high utilization rates of medical services and prescription drugs, and higher prevalence of workloss. Our estimates may be conservative as only patients diagnosed with abuse were included. To the extent that the abuse is prescription opioid abuse, payers should ensure appropriate access to opioids while considering abuse liability of drugs on formulary.