When urine specimens from a general tuberculosis patient population of 328 were submitted routinely for mycobacterial cultures, 33 patients (10 per cent) a positive turine cultures for Mycobacterium tuberculosis. In 22 patients (7 per cent) a positive urine culture for M. tuberculosis was unanticipated. Review of these 22 patients revealed that all had denied current genitourinary symptoms, 58 per cent had urinalyses within normal limits, and 58 per cent had normal intravenous pyelograms. Thus, lack of symptoms and normal tests do not necessarily exclude the possibility of genitourinary tuberculosis. Only 4.7 per cent of patients with pulmonary tuberculosis but 21 per cent of those with extrapulmonary tuberculosis had unanticipated positive urine cultures for M. tuberculosis. This suggests that routine submission of urine specimens for mycobacterial cultures can be a valuable adjunct to the bacteriologic confirmation of the diagnosis of extrapulmonary tuberculosis.