Four cases of acute glomerulonephritis associated with M-Type 57 streptococcus occurred at the Red Lake Indian Reservation during the summer of 1969. Prospective studies point to the skin as the initial site of infection in these patients. Two patients and four siblings were under continuous observation for more than a month before and after development of nephritis. In all patients with nephritis throat cultures were negative for Group A streptococci, and no pharyngitis preceded onset. In four of the six children from the nephritis family, the M-57 strain was isolated from normal skin sites before development of skin lesions. In all cases, appearance of the strain on the normal skin preceded recovery from the upper respiratory tract. In two patients with renal disease the nephritogenic strain reappeared on normal skin after antibiotic therapy, followed by recurrence of skin lesions due to Type 57 in one patient.