Fluconazole (Diflucan, CAS 86386-73-4) suppositories offer a novel way to administer this systemically active antimycotic. The pharmacokinetics and toleration of this new formulation have now been examined in healthy adult volunteers. In crossover experiments the bioequivalence was demonstrated for 200 mg suppositories and 200 mg capsules, and for 25 mg suppositories and 25 mg fluconazole in an oral suspension. The mean bioavailability of the 200 mg suppository relative to the capsule was about 93%. The mean bioavailability of the 25 mg suppository relative to the oral suspension was 107%. Absorption of fluconazole after administration of the suppositories was, however, somewhat slower than after oral ingestion of the capsule or suspension. The pharmacokinetic parameters of the 200 mg and 25 mg suppositories suggest that the kinetics of rectally administered fluconazole are linear with dosage. Daily administration of the 200 mg suppository gives a continuous increase in the mean fluconazole plasma concentration, until steady-state is reached on about the 5th day. The systemic and local toleration of the fluconazole suppositories was good.