Clinical and laboratory findings and drug history were studied in 17 patients with suspected hydralazine-associated nephritis, five of whom only had renal disease, while twelve also had extrarenal manifestations. Renal biopsies revealed extracapillary proliferative or focal segmental proliferative glomerulonephritis in 10 patients, and tubulo-interstitial nephritis in five patients. Antinuclear antibody (ANA) was found in 16 patients, but none of the 14 patients tested had antibodies to DNA. Tests for antibodies to myeloperoxidase (anti-MPO) and antibodies to neutrophil cytoplasm antigen (ANCA) were performed by ELISA. Twelve of the 14 patients tested had anti-MPO; five of these 14 patients had ANCA, while one had borderline levels. These findings suggest that hydralazine facilitates the induction of a systemic disease with multiple autoantibody production.