A selective HPLC method is described for the determination of cefpodoxime levels in plasma and sinus mucosa. Sample preparation included solid-phase extraction with a C8 cartridge. Cefpodoxime and cefaclor (internal standard) were eluted with methanol and analyzed on an optimised system consisting of a C18 stationary phase and a ternary mobile phase (0.05 M acetate buffer pH 3.8-methanol-acetonitrile, 87:103, v/v) monitored at 235 nm. Linearity and both between- and within-day reproducibility were assessed for plasma and sinus mucosa samples. Inter-assay coefficients of variation were lower than 13.6% (n = 10) for plasma (0.2 micrograms/ml) and lower than 12.4% (n = 5) for sinus mucosa (0.25 micrograms/g). The quantification limit was 0.05 micrograms/ml for plasma and 0.13 micrograms/g for tissue. The method was used to study the diffusion of cefpodoxime in sinus mucosa.