Population pharmacokinetics for gentamicin were compared with 20 Korean patients (14 male and 6 female) and 25 Caucasian appendicitis patients (16 male and 9 female). Two to six blood specimens were collected from all patients at the following times : just before a regularly scheduled infusion and at 0.5 hour after the end of a 0.5 hour infusion. Nonparametric expected maximum(NPEM) algorithm for population modeling was used. The estimated parameters were the elimination rate constant(K), the slope(KS) of the relationship between K versus creatinine clearance(Ccr), the apparent volume of distribution (V), the slope(VS) of the relationship between V versus weight, gentamicin clearance(CL) and the slope(CS) of the relationship between CL versus Ccr and the V. The output includes two marginal probability density function(PDF), means, medians, modes, variance, skewness, kurtosis, and CV%. The mean K(KS) were$0.402{pm}0.129hr^{-1}$ ($0.00486{pm}0.00197[hr{cdot}mL/min/1.73m^2]^{-1}$) and $0.425{pm}0.137hr^{-1}$($0.00432{pm}0.00168[hr{cdot}mL/min/1.73m^2]^{-1}$) for Korean and Caucasian populations, respectively. The mean V(VS) were not different at $14.3{pm}3.69L$($0.241{pm}0.0511L/kg$) and $15.8{pm}4.81L$($0.236{pm}0.0531L/kg$) for Korean and Caucasian populations, respectively (P>0.2). The mean CL(CS) were $5.68{pm}1.69L/hr$ ($0.0714{pm}0.0222L/kg[hr{cdot}mL/min/1.73m^2]$) and $6.29{pm}1.84L/hr$ ($0.0629{pm}0.0189L/kg[hr{cdot}mL/min/1.73m^2]$) for Korean and Caucasian populations, respectively. There are no differences in gentamicin pharmacokinetics between Korean and Caucasian appendicitis patients.