Summary30 patients with proven bladder malignant disease have been treated by Helmstein's hydrostatic pressure technique.Massive necrosis of tumour tissue has been shown to occur at cystoscopy, cytologically and on histological examination.Double contrast cystography can indicate reduction in tumour size within 2 weeks of treatment. Haematuria is usually stopped with diminution of frequency and dysuria.This treatment is suitable for large bulky T1tumours and advanced T4growths where palliation is the only treatment possible but not for T2and T3growths.Elderly and ill patients can tolerate this therapy easily and there were no serious side‐effects in this serie