A 19-year-old male developed nephrotic syndrome during the course of chronic osteomyelitis complicating a traumatic suppurative arthritis of the knee. Renal biopsy revealed severe mesangial proliferative glomerulonephritis, and immunofluorescent microscopy demonstrated the presence of IgA. Nephrotic syndrome remitted during the treatment for chronic osteomyelitis, suggesting a close association of the two conditions.