A study of renal tumours filed in the pathology department of a regional hospital in Hong Kong during 1971-1990 showed 6 cases of surgical emergency due to spontaneous rupture of the kidney by tumour. All occurred as a complication of renal angiomyolipoma, a rare tumour or hamartoma. A literature review showed that the renal tumour most frequently reported to cause spontaneous rupture was renal carcinoma. Chinese patients appear to have more renal ruptures due to angiomyolipoma than to renal carcinoma. It is proposed that intra-operative frozen section diagnosis should be sought, when this can be safely performed, in cases of rupture of the kidney by tumour. Surgery aiming at conserving functional renal parenchyma is appropriate for benign lesions such as angiomyolipoma.