Clear cell sarcoma of the kidney (CCSK) is a distinct, highly malignant renal tumour of childhood which was diagnosed in 5 (3.9%) of 133 primary renal tumours in children under 15 years of age in the period from 1976 to 1990. The clinical and pathological features of these patients are presented. The most common clinical features were abdominal mass and haematuria. The male to female ratio was 1: 1.5 and there was predilection for the left side (4:1). The age of patients varied from 5 months to 4 years (average age 23 months). In four children the tumour was in Stage I, and in one child in Stage II. Three tumours showed classical microscopic pattern of CCSK. The treatment for all patients consisted of preoperative chemotherapy, radical surgery and additional aggressive chemotherapy. Four patients developed metastases: three of them to bones and one to the liver. Three patients died of the tumour, one is alive but with the tumour (3 years follow-up), and one child is alive and without any evidence of disease (3-years follow-up). Although relatively uncommon, these tumours are responsible for 50% of all children's deaths from renal tumours and, so, their precise classification is essential for proper treatment.