Abstract A 37-year-old man presented with biopsy-proved rapidly progressive glomerulonephritis and a strongly positive fluorescent treponemal antibody result. The patient was treated with hemodialysis, plasmapheresis, methylprednisolone, and penicillin, with rapid improvement and stabilization of renal function. Antibody was eluted from the frozen renal tissue and demonstrated a strongly positive reaction to the treponemal antigen when used in the fluorescent treponemal antibody test. In addition, when specific rabbit antitreponemal antiserum was applied to the frozen renal sections, there was a strongly positive reaction. Although syphilis has been associated with membranous glomerulopathy and post-infectious glomerulonephritis, this appears to be the first case of latent syphilis in which rapidly progressive glomerulonephritis has been identified. The presence within the glomeruli of treponemal antigen and antitreponemal antibody supports the association of these two entities.