The pharmacokinetics of netobimin (NTB) metabolites has been investigated in ewes. Non-pregnant ewes and ewes in the first and last third of pregnancy were dosed orally with 20 mg kg bodyweight of NTB. Blood samples were collected from the jugular vein from 30 minutes to 72 hours after administration and plasma samples were analysed by high performance liquid chromatography. Neither NTB nor albendazole (ABZ) were detected in any of the samples analysed. No statistically significant differences were found between the pharmacokinetic parameters of albendazole suphoxide (ABZSO) and albendazole sulphone (ABZSO2) among the three groups of ewes. The peak plasma concentrations (C(max)) ABZSO and ABZSO2 were reached about 10 and 20 hours respectively after administration in all three groups. The ratios of ABZSO/ABZSO2 for C(max) and the areas under the curve (AUC(0-α)) were 6 and 3, respectively, in each group and suggest a low rate of oxidation of sulfoxide to sulphone.