To assess and compare epidemiological factors, clinical and radiological signs, laboratory results and drug resistance in patients with tuberculosis (TB) with and without AIDS. Retrospective study of TB diagnosed bacteriologically between January 1993 and December 1996 at Hospital Universitario La Fe. Annual rates were 41.7, 47.1, 34.6 and 43.8 per 100,000 inhabitants in 1993 to 1996, respectively. AIDS was present in 22.4%. TB was pulmonary in 87% and 49.4% in patients without and with AIDS, respectively. Incidence was higher in the 25 to 34 age range. Prior contact with TB patients was established in 19.2% of cases. Pulmonary TB in patients with AIDS presented with normal lung X-rays in 30.1%; 16.2% of these had positive sputum cultures. Pulmonary cavitation was evident in 32.6% of TB patients without AIDS and 6.8% of those with AIDS. Pulmonary TB was diagnosed by culture of sputum taken at the time of admission in 25.9% of non AIDS patients and in 12.4% of patients with AIDS. Extrapulmonary TB was diagnosed by culture in most cases. Such forms predominated among TB plus AIDS patients, with most cases being ganglial and urogenital. Overall drug resistance was 8.3% (7.4% non-AIDS/11.5% AIDS). Primary resistance (PR) was 6.3% and 7.1%, PR to hydrazides was 5% and 5.4%, and secondary resistance was 32.4% and 33.3%. Drug resistance in non-AIDS and AIDS patients, was associated with a history of TB and past treatment (p < 0.009), prior contact with TB patients (p < 0.004) and pulmonary cavitatin (p < 0.02). TB with AIDS tends to occur in a younger population, is often extrapulmonary or with atypical lung involvement. Drug resistance is similar in patients with and without AIDS.