Fluorescein isothiocyanate conjugated rabbit antibodies to keratinase II were used to detect keratinase II and antibodies to keratinase II in sections of previously infected guinea pig skin. The presence of the enzyme or an antibody reaction to the enzyme was indicated by a perifollicular pattern of green fluorescence at the level of the external root sheath of the hair follicle. The results indicate that keratinase II is produced during infection with T. mentagrophytes var. granulosum. There is a local reaction to the enzyme in tissue which is also observed at the injection site following immunization with active keratinase II.