Eleven cases of bladder cancer were observed at the National Spinal Injuries Centre out of 3800 paraplegic and tetraplegic patients treated since 1944. There were nine men and two women: the average age of the patients was 51 years. Seven patients were flaccid and four spastic. Diagnosis was made 13-42 years after the onset of paraplegia. Haematuria was the first symptom in seven cases. Cystography showed filling defect in two cases. With regard to the aetiology of bladder cancer various carcinogenic factors are discussed. Occupational exposure as well as smoking and hereditary causes could be excluded. The only common factor in all these patients was long-standing, chronic bladder infection. Moreover all patients had either long-standing suprapubic or urethral drainage by indwelling catheter. In order to facilitate early diagnosis of bladder cancer, cytological examination of urine for cancer cells are carried out systematically at the National Spinal Injuries Centre. Since 1965 out of 374 cases examined, only one was found to be positive, and biopsy and later necropsy confirmed cancer of the bladder.