Differential-pulse adsorptive stripping voltammetry was used to determine ceftriaxone in serum and aqueous humour samples. The method involved extraction of the ceftriaxone from serum samples with an Amberlite XAD-2 column followed by elution with methanol. The recovery was 97.6% with a relative standard deviation of 3.3% at a ceftriaxone concentration of 90.9 mu g l(-1). Peak currents of ceftriaxone were measured with a hanging mercury drop electrode at -0.78 V versus an Ag-AgCl reference electrode in pH 3.0 Britton-Robinson buffer. The calibration graph was linear from 0.02 to 1300 mu g l(-1). The method was applied to cataract cases and ceftriaxone levels were measured in aqueous humour and serum samples from patients who had received 1 or 2 g of ceftriaxone intravenously. Aqueous humour was added to the polarographic cell directly. The amounts of ceftriaxone in the aqueous humour and serum samples with respect to time were measured. The pharmacokinetic profiles for 1 and 2 g were compared.