We have reviewed the clinical histories of 1,815 immunocompromised patients seen in "La Paz Hospital" over a period of 6 years, in order to study the incidence and clinical forms of tuberculosis (TB) in this group of patients. We have distributed the patients into three groups: Group A: 1,372 patients with neoplasia, Group B: 173 patients under immunosuppressor treatment, and Group C: 270 intravenous drug abusers (IVDA). 53 patients developed TB (2.9%): Of these, 31 belonged to group A (2.25%), 14 to group B (5.78%) and 8 to group C (2.96%), resulting in an incidence 50 to 100 times greater than the calculated for the Spanish general population (0.05%). There is a greater incidence of extrapulmonary and atypical forms in IVDA and patients under immunosuppressor treatment. Patients with neoplasia do not present differences in these aspects with regard to immunocompetent patients. If the TB is diagnosed and treated on time it is a potentially curable disease and the immunosuppressed state does not condition a worse response to treatment.