The effects of estrogen (E) on memory were assessed in 19 women who required a hysterectomy and bilateral oophorectomy for benign disease. Blood samples were drawn and memory tests were administered before surgery and again after 2 mo of postoperative treatment consisting of either monthly E or placebo (PL) injections. Scores on the immediate and delayed recall of paired-associates stayed at the same level in E-treated women, whereas they decreased significantly pre- to post-operatively in the PL-treated subjects. In the immediate recall of paragraphs, the scores of those given E improved postoperatively compared to baseline; scores remained unchanged in the PL group. No hormonal effects were apparent on the immediate or delayed recall of visual material, delayed recall of paragraphs, or digit span scores. These findings suggest that variations in specific aspects of memory function may occur in surgically menopausal women coincident with changes in plasma estrone and estradiol levels.