We have compared diazepam pharmacokinetics in 16 Chinese and 18 white Caucasian healthy male volunteers, resident in Hong Kong and have correlated them with physical attributes. Serum concentrations of diazepam and desmethyldiazepam were measured in venous blood by an enzyme-linked immunoassay (0–3 h samples) and HPLC (3–72 h samples). Pharmacokinetic parameters were derived assuming a two compartment model, distribution phase <6 h,="" and="" 100%="" oral="" systemic="" availability.="" compared="" with="" the="" chinese="" the="" white="" caucasians="" were="" older,="" heavier,="" taller,="" and="" fatter,="" as="" judged="" by="" skin="" fold="" thickness="" (sft)="" and="" total="" body="" weight="" to="">Ideal body weight (TBW/IBW) ratio; respective mean differences being 16%, 27%, 4%, 26%, and 15% (p<0.05). mean="" diazepam="" apparent="" volume="" of="" distribution="" (v)="" and="" v/ibw="" were="" larger="" in="" the="" white="" caucasians="" (52%="" &="" 39%="" respectively,="">p=0.002). SFT and TBW/IBW ratio yielded the best correlations with V, V/TBW and V/IBW (0.50–0.75, p<0.05). obesity="" indices="" contributed="" most="" to="" the="" overall="" regressions="">² up to 0.52), and for V there was a further small effect (2%, partial F test) due to ethnic group, possibly reflecting stature. Mean peak diazepam concentration (C_max) was similar in both ethnic groups. Time to C_max (t_max) was more often prolonged in the Chinese (X ² test, p=0.01). Body fat and stature may thus account for these inter-ethnic differences in the apparent volume of distribution of diazepam, a highly lipid-soluble drug.