The alterations in lectin fluorescence stainings to the epidermis were examined in guinea pig skin treated with topical application of a 1% 8-methoxypsoralen (8-MOP) solution plus long-wave ultraviolet (UVA) radiation (1.5-3.5 J/cm2) (PUVA). Serial biopsy specimens taken up to 21 days postirradiation were stained with 8 commercially available lectins labeled with either fluorescein isothiocyanate (FITC) or biotin (followed by avidin D-FITC): Bandeiraea simplicifolia agglutinin I (BSA), concanavalin A (Con-A), Dolichos biflorus agglutinin (DBA), peanut agglutinin (PNA), Ricinus communis agglutinin I (RCA), soybean agglutinin (SBA), Ulex europeus agglutinin I (UEA), and wheat germ agglutinin (WGA). In normal guinea pig skin UEA staining was absent. Following PUVA treatment, UEA and DBA stainings became apparent or stronger in intensity after days 7-14 (UEA) and days 4-7 (DBA), respectively, and returned to negative or weak by days 14-21. Stainings with Con-A, SBA, and WGA gave remarkable decreases in intensity after days 2-4 and recovered to the baseline by days 7-14. Intensity of BSA, PNA, and RCA stainings was decreased to a lesser degree than the other lectins. Such changes were not produced by application of 8-MOP, UVA radiation (less than 10 J/cm2), UVB radiation (900-2700 mJ/cm2), or tape stripping. These results suggest that PUVA treatment perturbs the composition or organization of epidermal cell surface glycoconjugates to induce alterations in lectin stainings.