Mometasone furoate (SCH 32088) is a synthetic corticosteroid which has a topical anti-inflammatory activity with a minimal potential for suppressing hypothalamic-pituitary-adrenocortical (HPA) axis. A sensitive competitive enzyme immunoassay (EIA) for measuring SCH 32088 in unextracted human plasma has been developed. The 3-(O-carboxymethyl)oxime (CMO) of SCH 32088 was synthesized and conjugated with bovine thyroglobulin, and the product was used for the production of antibodies in rabbits. SCH 32088-3-CMO was also conjugated with horseradish peroxidase, which was used as the tracer. The EIA thus developed can detect 1 pg SCH 32088 per assay or 25 pg per ml of human plasma. It can reliably quantitate SCH 32088 in human plasma from 50 pg ml-1 to 2.5 ng ml-1 with good linearity, accuracy and precision. The assay can be extended to measure SCH 32088 in plasma of laboratory animals. The availability of this sensitive assay makes it possible to evaluate the pharmacokinetics and toxicokinetics of SCH 32088 in laboratory animals and man.