Population pharmacokinetics for gentamicin were compared with 24 American patients (16 male and 8 female) and 16 Korean-American appendicitis patients(12 male and 4 female). Two to six blood specimens were collected from all patients at the following times: just before a regularly scheduled infusion and at 1/2 hour after the end of a 1/2 hour infusion. Nonparametric expected maximum(NPEM) algorithm for population modeling was used. The estimated parameters were the elimination rate constant(K), the slope of the relationship between K versus creatinine clearance(KS), the apparent volume of distribution(V), the slope of the relationship between V versus weight(VS), gentamicin clearance(CL) and the slope of the relationship between CL versus creatinine clearance and the VS(CS). The output includes a 3-dimensional plot of the joint probability density function(PDF), two marginal PDF, means, medians, modes, variance, skewness, kurtosis, and CV%. The mean K(KS) were 0.424$pm$0.139(0.00429$pm$0.00164) and 0.411$pm$0.135 hr$^{-1}$ (0.00475$pm$0.00180[hr.mL/min/1.73m$^{2}]^{-1}$) for American and Korean-American populations, respectively. The mean V(VS) were not different at 15.6$pm$4.77(0.233$pm$0.0526) and 15.1$pm$3.84L(0.239$pm$0.0492 L/kg) for American and Korean-American populations, respectively (P>0.2). The mean CL (CS) were 6.28$pm$1.85(0.0634$pm$0.0191) and 5.70$pm$1.77 L/hr(0.0701$pm$0.0215 L/kg[hr.mL/min/1.73m$^{2}$)] for American and Korean-American populations, respectively. There are no differences in gentamicin pharmacokinetics between American and Korean-American Appendicitis patients.