Eclampsia occurring more than 48 hours postpartum has been observed in an unusual number of patients. From August 1977 to November 1982 at E. H. Crump Women's Hospital and Perinatal Center (Memphis), there were 132 documented cases of eclampsia, of which 36 (27%) occurred postpartum. Seventeen (47%) of these occurred more than 48 hours postpartum. Preeclampsia was diagnosed before the onset of convulsions in 12 patients, all of whom received intravenous magnesium sulfate postpartum. The mean duration of postdelivery magnesium sulfate therapy was 32 hours (range 24 to 72 hours). Headaches and visual disturbances were reported by all 17 patients before onset of convulsions. Physical and laboratory findings immediately after the convulsions were consistent with eclampsia. Treatment consisted primarily of intravenous magnesium sulfate. Neurologic consultation was obtained to rule out a neurologic disorder, and metabolic studies were also done. Electroencephalograms were done on 15 patients; eight of them showed patterns consistent with encephalopathy.