This article presents information on immunofluorescence (IF) studies which afford valuable adjuncts to clinical and histologic examinations, particularly in vesicuiobullous and connective tissue diseases, and to some extent in immune complex disturbances and certain other skin diseases. Both serum studies by indirect IF tests and skin biopsy examinations by direct IF staining can provide diagnostic information. Studies of vesicuiobullous diseases call for biopsies primarily of clinically normal or nonbullous skin adjacent to lesions.