The demographics of tuberculosis (TB) and the therapy of malignancies have significantly changed since the last comprehensive review of TB in cancer patients. Fifty-six patients with both TB and malignancy were identified from January 1989 through December 1994 in a population of 61,931 newly registered cancer patients. The frequency of TB in cancer patients was 90 per 100,000. TB was more frequent in foreign-born patients (p < 0.001) and in racial and ethnic minorities (p < 0.001) than in non-Hispanic whites. TB developed during therapy in 48%. TB was discovered synchronously with the malignancy in 30% and in 21% occurred > or = 18 months after therapy. Pulmonary TB occurred in 50 (89%) patients and extrapulmonary TB in nine (16%) (three had both). Chest radiographic findings did not suggest TB in 20%. TB was less frequent in lung cancer (p < 0.001), head and neck cancer (p = 0.002), and solid hematologic malignancies (p < 0.001) than it had been historically, but the frequency was unchanged in acute leukemia patients (p = 0.46). TB in cancer patients occurs at a nine times greater than in the general population. It is now most frequent in leukemia patients.