A new method for delayed contact hypersensitivity assay of chemical compounds in guinea pigs, a short-period method (14 days) with a high detection sensitivity, has been developed. The new method was as follows; a combination of a Freund's complete adjuvant (FCA, undiluted) intradermal injection and a 24-h occlusive patch on a guinea pig was performed 2x at an interval of 4 days and challenged by non-occlusive topical application 11 days after the first sensitization (with benzyl alcohol during test development). Acanthosis and spongiosis in the epidermis and mononuclear cell infiltration into the dermis were observed histopathologically at the skin reaction site. This newly developed method (adjuvant and 24-h occlusive patch 2x test: AP2 test) could equally and/or better detect the allergenicities of 6 other chemical compounds (bromostyrol, citronellal, benzyl salicylate, p-aminobenzoic acid ethyl ester, p-phenylenediamine and formaldehyde) as compared with the cumulative contact enhancement test (CCET) and the guinea pig maximization test (GPMT).