To study the relationship between metabolic phenotype of acetylation and bladder cancer Methods Totally 203 healthy volunteers and 67 patients with bladder cancer were investigated with caffeine as a metabolic probe Urine samples were collected in 2-6 hours after a cup of 140?mg coffee was taken, and the caffeine metabolites, 5 acetylamino 6 formylamino 1 methyluracil (AFMU) and 1 methylxanthine (1X) were analyzed by high performance liquid chromatography (HPLC) The frequency histogram and probit plot were constructed to select the critical value which was used to assess slow and fast acetylation status both in healthy volunteers and patients with bladder cancer Results The peak height ratios of AFMU and 1X (AFMU/1X) were from 0 06 to 6 50 for healthy volunteers and 0 10 to 6 31 for patients with bladder cancer, both with the critical value of 1 10 Of 203 healthy volunteers involved in this study, 26 3% were slow acetylacors, as compared to 46 3% with slow acetylacors in patients with bladder cancer The odds ratio is 2 376, and the gene frequency for healthy volunteers and patients with urinary bladder cancer were 0 5218 and 0 6804, respectively Conclusions N acetylation status in the Chinese population is polymorphic and completely concordant with that determined with other metabolic probes Slow acetylators are significantly associated with bladder cancer To study the relationship between metabolic phenotype of acetylation and bladder cancer Methods Totally 203 healthy volunteers and 67 patients with bladder cancer were investigated with caffeine as a metabolic probe Urine samples were collected in 2-6 hours after a cup of 140? Mg coffee was taken , and the caffeine metabolites, 5 acetylamino 6 formylamino 1 methyluracil (AFMU) and 1 methylxanthine (1X) were analyzed by high performance liquid chromatography (HPLC) The frequency histogram and probit plot were constructed to select the critical value which was used to assess slow and fast acetylation status both in healthy volunteers and patients with bladder cancer Results The peak height ratios of AFMU and 1X (AFMU / 1X) were from 0 06 to 6 50 for healthy volunteers and 0 10 to 6 31 for patients with bladder cancer, both with the critical value of 1 10 Of 203 healthy volunteers involved in this study, 26 3% were slow acetylacors, as compared to 46 3% with slow a cetylacors in patients with bladder cancer The odds ratio is 2 376, and the gene frequency for healthy volunteers and patients with urinary bladder cancer were 0 5218 and 0 6804, respectively Conclusions N acetylation status in the Chinese population is polymorphic and completely concordant with that determined with other metabolic probes Slow acetylators are significantly associated with bladder cancer