Malnutrition is associated with morbidity and mortality in HIV-infected individuals. Little research has been conducted to identify the roles that clinical, illicit drug use and socioeconomic characteristics play in the nutritional status of HIV-infected patients. This cross-sectional analysis included 562 HIV-infected participants enrolled in the Nutrition for Healthy Living study conducted in Boston, MA and Providence, RI. The relationship between body mass index (BMI) and several covariates (type of drug use, demographic, and clinical characteristics) were examined using linear regression. Overall, drug users had a lower BMI than non-drug users. The BMI of cocaine users was 1.4 kg/m(2) less than that of patients who did not use any drugs, after adjusting for other covariates (p=0.02). The BMI of participants who were over the age of 55 years was 2.0 kg/m(2) less than that of patients under the age of 35, and BMI increased by 0.3 kg/m(2) with each 100 cells/mm(3) increase in CD4 count. HAART use, adherence to HAART, energy intake, AIDS status, hepatitis B and hepatitis C co-infections, cigarette smoking and depression were not associated with BMI in the final model. In conclusion, BMI was lower in drug users than non-drug users, and was lowest in cocaine users. BMI was also directly associated with CD4 count and inversely related to age more than 55 years old. HIV-infected cocaine users may be at higher risk of developing malnutrition, suggesting the need for anticipatory nutritional support.