Between the extremes of radical (total) cystectomy and deep X-radiation for carcinoma of the bladder urologists have been sustained by the experienced knowledge that full thickness removal of an adequate amount of bladder wall can prove a very satisfactory treatment for any growth of suitable size. A method is here described which allows at least hemicystectomy and bladder wall is replaced by peritoneal flap. The method is safe and simple, and although peritoneal replacement is obviously not required for a small tumour it gives the surgeon confidence to know that he need not leave a very small bladder after removing a large area of wall, remembering too that it is advisable to take more not less free fringe with the larger tumour.