Hexyl aminolevulinate, the hexyl ester of 5-aminolevulinic acid, is a photosensitising agent designed to enhance the detection of bladder cancer tumours, in particular highly malignant carcinoma in situ (CIS). After cellular uptake, hexyl aminolevulinate and/or hydrolysed 5-aminolevulinic acid enter the haem biosynthetic pathway and induce accumulation of the photoactive compound protoporphyrin IX (PpIX) in malignant as opposed to nonmalignant cells. PpIX emits red fluorescence when illuminated under blue light. Blue-light fluorescence cystoscopy with hexyl aminolevulinate (hexyl aminolevulinate cystoscopy) was more effective than standard (white-light) cystoscopy for detecting non-muscle-invasive ('superficial') disease in two European, multicentre, phase III trials, which evaluated hexyl aminolevulinate cystoscopy as an adjunct to standard cystoscopy in patients with known or suspected bladder cancer. In one trial, hexyl aminolevulinate cystoscopy detected 96% of the patients with CIS; it identified 28% more patients with CIS than standard cystoscopy. In the other trial, 17% of patients were selected to receive more complete treatment following hexyl aminolevulinate cystoscopy than standard cystoscopy, because of the improved tumour detection rate. Hexyl aminolevulinate cystoscopy is well tolerated as an adjunct to standard cystoscopy; adverse events were those typically associated with standard cystoscopy/biopsy (e.g. postoperative pain).