Soft tissue infections (STI) and abscesses are a common complication of injection drug use (IDU). Health care utilization to treat these infections is a significant source of cost to society. The extent of this cost in Los Angeles County is unknown. This retrospective chart review investigated the magnitude and health service utilization patterns of IDU associated STI admissions at Los Angeles County USC Medical Center (LAC+USC), comparing STI admissions with STI admissions unrelated to IDU (NIDU). 150 charts - 50 per year - were randomly selected from a list of STI admissions to LAC+USC between 3-1-2000 and 3-1-2003. Patient demographics, clinical characteristics, clinical course, and discharge disposition were abstracted from each chart. We found 47 of these 150 charts represented patients admitted with IDU associated STIs (31.5%). Patients admitted with IDU associated STIs were significantly more likely than NIDU STIs to be homeless (38.3% v. 21.6%), be non-Hispanic/Latino (80.8% v. 32.3%), have Hepatitis B (8.5% v. 1.0%) or C (40.4% v. 2%), have an infection complicated with abscess (47.5% v. 36.3%), have had prior antibiotic treatment (14.9% v. 31.7%), and have left Against Medical Advice (17.0% v. 7.8%). IDU and NIDU STI admissions were not significantly different in age, mean length of hospital stay, probability of operating room procedure, or prevalence of Methicillin-Resistant-Staphylococcus-aureus or HIV infection. We conclude that a significant proportion of STI admissions to LAC+USC are IDU-related. These patients have higher health service utilization than their NIDU counterparts and may benefit from improved pre-hospital care services. Reducing the number of IDU associated STIs in Los Angeles Country is likely to significantly reduce LAC+USC's costs.