Anaphylactoid shock, disseminated intravascular coagulation, and anuric renal failure requiring dialysis occurred in a patient receiving zomepirac sodium for toothache. Although renal function showed gradual improvement after seven days of anuria, the recovery was slow and incomplete. Renal biopsy three weeks after the onset of renal failure revealed evidence of focal renal cortical necrosis. Association of zomepirac administration with renal cortical necrosis is not known to have been previously demonstrated. This observation adds another dimension to the previously reported renal complications of nonsteroidal anti-inflammatory agents, especially zomepirac. The proportions of lymphocyte subsets, as defined with monoclonal antibodies, and the proliferative response to mitogens were normal. The patient's lymphocytes showed no proliferative response to zomepirac. Serum complement components and immunoglobulin levels were within normal limits, and radioallergosorbent testing gave negative results. The mechanism of anaphylactoid reaction to zomepirac in this case, therefore, remains unclear.