Gabapentin, 1-(aminomethyl-1-cyclohexyl)acetic acid, is anew antiepileptic drug related to ${gamma}-aminobutyric$ acid(GABA) currently being introduced in therapy worldwide. The bioavailability and pharmacokinetics of gabapentin capsules were examined in 22 volunteers who received a single oral dose in the fasting state by randomized balanced $2{ imes}2$ crossover design. After dosing, blood samples were collected for a period of 24 hours and analyzed by liquid chromatography-tandem mass spectrometry (LC/MS/MS). Time course of plasma gabapentin concentration was analyzed with non-compartmental and compartmental approaches. $WinNonlin^{(R)}$, the kinetic computer program, was used for compartmental analysis. One compartment model with first-order input, first-order output with no lag time and weighting by $1/(predieted;y)^2$ was chosen as the most appropriate pharmacokinetic model for the volunteers. The major pharmacokinetic parameters $(AUC_{0-24hr},;AUC_{inf},;C_{max};and;T_{max})$ and other parameters $(K_a,;K_{el},;V_d/F;and;Cl/F)$ of $Gapentin^{TM}$ (test drug) and $Neurontin^{TM}$ (reference drug) were estimated by non-compartmental analysis and compartmental analysis. The 90% confidence intervals of mean difference of logarithmic transformed $AUC_{0-24hr};and;C_{max}$ were $log(0.9106){sim}log(1.l254);and;log(0.8521){sim}log(1.0505)$, respectively. It shows that the bioavailability of the test drug is equivalent with that of the reference drug. There was no statistically significant difference between the two drugs in all pharmacokinetic parameters.