Abstract: Aim Acetylator status of 203 healthy controls and 67 patients with bladder cancer was observed.Methods All the subject s w ere N-acetylate-phenotyped with caffeine asametabolic probe drug.Urine samples were collected 2 hours after a cuPof 140mg-caffeine-spiked coffee was taken under fasting condition in the morning.The caffeine metabolites,5-acetylamino-6-formylamino-1-me thyluracil(AFMU) and 1-methy lxanthine (1X)were analysed by High Performance Liquid Chromatog raphy(HPLC).The frequence histogram and probit plot were constructed to select the antimode which was used to assess slow and fast acetylator statusboth in healthy controls and patients with bladder cancer.Results The peak hight ratios (PHR)of AFMU/1X were from 0.06 to 6.5 for healthy voluteers and 0.1 to 6.31 for patients with bladder cancer.Of the 203 healthy controls involved in this study 73.7%(149/203)had the AFMU/1X>1.10,and were classified as fast acetylators,and 26.3%(54/203)as slow acetylators,while 53.7%(36/67)were fast acetylators and 46.3%(31/67)were slow acetylators in patients with bladder cancer.The oddsratio was 2.376,and the genefreqency for healthy controls and for patients with urinary bladder cancer was 0.51 and 0.68 respectively.Conclusion The acetylator status of Chinese population is polymorphic and completely in concordance with that determined by dapsone,isoniazid or sulfamethazine methords as previously reported.Slow acetylators might be susceptible to urinary bladder cancer.

Key words: N-acetylation, polymorphism, bladder cancer, caffeine