Four cases of costal chondrosarcoma were observed in the Thoracic Surgery Department of Nostra Señora de Aránzazu Hospital in San Sebastián. This tumour rarely occurs in the ribs and no papers concerning more than one personal case, over such a brief interval, have been reported. The diagnosis was established on the basis of clinical and radiological data in three cases and after biopsy in the fourth case. Large surgical resection allowed complete histological examination, which confirmed the diagnosis of chondrosarcoma. The tumours were classified into grade I and II according to the degree of differentiation of the tumour cells. All 4 patients were treated exclusively by surgical resection. Marlex mesh was necessary to repair the chest wall defect in 3 cases. The functional result was satisfactory. One of these patients was lost to follow-up and no signs of recurrence have been observed in the other 3 patients, although the follow-up remains relatively short (9, 8 and 7 months, respectively).