Patellar foci of any origin are very rare. Form 1955 to the end of 1979, 9 patients underwent patellar surgery in our hospital. 7 of these patients had tuberculosis, whereas in one case the patient had chronic nonspecific osteomyelitis, and in one case we were unable to clarify the underlying cause of the focus, neither from the histological nor from the bacteriological aspect. All tuberculous foci, one of which had penetrated into the knee joint, were situated in the corpus of the patellar. In a 10-year old girl, the entire patellar was infected with tuberculous foci. In the anterior-posterior x-ray film, the processes mainly presented a circular appearance. Their diameter different between 6 and 25 mm. In one of the foci, two sequesters were conspicuous, and one in another patient. 6 of the patients had an active organ tuberculosis at the same time, or reported on a specific disease during anamnesis. The period from the onset of complaints until diagnosis had been established, was on the average 14.4 months with the 7 patients under investigation (average age 29 years, 4 female/3 male). In view of the fact that all the patients reported here were late cases, the results of the combined drug and surgical removal of foci (filling of the surgical cavities with spongiosa) must be classified as good. One knee joint had to be stiffened by operation. There were no reactivations within an average followup period of 3 years.