Cystine stone material was collected from 27 patients treated in various hospitals in Finland. The prevalence of cystine stones was found to be one/year/1,000,000 inhabitants. A total of 49 operations were performed on 20 patients, with five nephrectomies carried out as the first stage of treatment in the patients with stones. Extracorporeal shock wave lithotripsy (ESWL) failed to fragment cystine stones in one patient and percutaneous stone removal was necessary. The delay in the diagnosis of cystinuria averaged 5.1 years. Most patients with cystine stones had homozygous cystinuria. Anuria due to recurrent stone formation occurred in three patients. Chronic urinary tract infection was seen in nine out of 15 (60%) women patients and four of these nine had inflammatory changes in the kidneys diagnosed by urography. Early diagnosis of cystinuria is important to avoid kidney injury and recurrence of cystine stones.