Pharmacokinetic profiles of pentylenetetrazol in the dog were studied following rapid intravenous and oral administrations of a convulsant dose (15-20 mg/kg). Plasma level-time curves after a rapid intravenous injection showed biexponential decline, indicating that the disposition of this drug in the dog follows a two-compartment body model. Pharmacokinetic parameters were calculated from the intravenous data. After oral administration of the solution dose, the peak plasma level appeared at about 30 min postdose, indicating that the absorption occurs rapidly. Areas under the oral plasma level-time curves s howed that the drug was absorbed completely and that the first-pass metabolism effect was minimal. The ligation studies of the kidney and the liver suggested that the main elimination pathway of this drug was biotransformation in the liver. The average plasma half-life was 1.4 hr. At steady state, the volume of distribution was approximately equivalent to the volume of the total body water.