One-hundred and five hydrostatic distensions of the bladder (HDB) were carried out in 89 patients. The technique is simple, and complications were uncommon: 3 cases of bacteraemia and 4 cases of ruptured bladder. No death was recorded. The main indication was tumour of the bladder (76 patients). Satisfactory results, with reduction or complete disappearance of the lesions, were obtained in superficial, non-infiltrating tumours, but in type B tumours invading the vesical muscle failures were almost constant. Eight patients with pronounced reduction of bladder capacity were also treated by HDB with varying results depending upon the underlying cause. Two out of 3 patients with severe frequencies and normal-size bladder were relieved by the treatment. HDB was also successfully used in 2 patients with intractable vesical haematuria.