A cross-sectional study was conducted to estimate HIV seroprevalence among infectious (smear positive) cases of pulmonary tuberculosis and to describe the relation between antituberculosis drug resistance and infection with human immunodeficiency virus. A total of 418 smear positive pulmonary tuberculosis patients who attended the out patient departments of Harar Tuberculosis Centre and two general hospitals were studied from October 1994 through January 1995. The majority (94%) of these patients were from the tuberculosis centre. Sputum cultures were positive for 338/418 (80.9%) patients. HIV seroprevalence was 92/418 (22.0%) among smear positive and 69/338 (20.4%) among culture positive patients. HIV positive patients were more likely to be from urban than rural areas (p < 0.001). Initial resistance was not affected by HIV seropositivity. Secondary drug resistance was significantly higher in HIV positive patients than HIV negatives (p < 0.05). Although not significant, HIV positive patients were more defaulters than HIV negatives. Significantly higher numbers of HIV positive pulmonary tuberculosis patients were cases of relapse and treatment failure (p < 0.05). Other studies are required in order to assess the impact of HIV infection on the spread of anti-tuberculosis resistance. Supervised and appropriate treatments with follow up are required in order to minimise the spread of drug resistant tubercle bacilli among HIV infected patients.