The natural menopause is not associated with substantial cognitive change. Limited clinical trial evidence suggests that estrogen-containing hormone therapy has little effect on cognition during midlife, but prompt initiation after surgical menopause may improve aspects of memory. Among older postmenopausal women, strong clinical trial evidence demonstrates that hormone initiation does not improve cognition. More limited clinical trial evidence indicates no improvement in Alzheimer symptoms, and the Women's Health Initiative Memory Study found an increase in dementia risk among older women. Observational findings of reduced Alzheimer risk may reflect early hormone use in younger women, or findings may be biased. Cognitive effects of selective estrogen receptor modulators are not yet well studied.