OBJECTIVE: To determine the use of hypericin instillation for the fluorescent detection of papillary bladder cancer and carcinoma in situ. PATIENTS AND METHODS: Eighty-seven patients with papillary bladder cancer and/or carcinoma in situ received instillations with 40 mL of an 8 micromol/L hypericin solution for at least 2 h. Fluorescent excitation with blue light was effective for up to 16 h, and biopsies were examined by fluorescence microscopy. RESULTS: There were no side-effects reported, no photobleaching and all papillary lesions fluoresced red. The sensitivity and specificity for detecting carcinoma in situ was 94% and 95%, respectively. An interval of 4 months is recommended after BCG instillations before using this test. Fluorescence microscopy showed that hypericin was selectively localized in the epithelium. CONCLUSIONS: Hypericin-induced fluorescence has a high sensitivity and specificity for detecting bladder cancer. After 4 months there are few false-positive results in patients treated with BCG.