Studies of the epidemiology of acute glomerulonephritis (AGN) following pyoderma reported over the past 15 years have been reviewed. Investigations in Alabama, at Red Lake in Minnesota, and in Trinidad proved of special interest because they contribute new information concerning the natural history of streptococcal skin infections and the role of such infections in AGN. Interesting contrasts between streptococcal infections of the skin and those of the throat are now apparent. Compared with pharyngeal infections, skin infections are more common in young preschool children, are caused by different serotypes, and differ in the nature of the streptococcal antibody response. A number of new M-serotypes of group A streptococci, including several of importance in AGN, were found in studies of pyoderma. In contrast to M-types 1 and 12 (those of major importance in AGN followng pharyngitis), M-types 2, 49, 55, 57, and 60 are now recognized to be of major importance in AGN following pyoderma. Although streptococcal skin infections are quire important in AGN, they do not result in acute rheumatic fever.