Objectives To determine patterns and prevalence of sexual behavior, problems, and attitudes in individuals with different cognitive status. Design We used data from the National Social Life, Health, and Aging Project to describe the relationship between sexual behavior, function, and cognitive status (normal, mild cognitive impairment, dementia), classified using an adapted Montreal Cognitive Assessment (MoCA) (0?30 points). Setting U.S. home-dwelling older adults. Participants Nationally representative probability sample of 3,196 adults (1,682 women, 1,514 men) aged 62 to 91 (mean 72). Measurements Cognitive status and sexual activity, problems, and attitudes. Results The weighted response rate was 74%. Mean MoCA score was 22.7. Of partnered people with dementia, 59% of men and 51% of women were sexually active, including 41% of those aged 80 to 91; 46% of all men (95% confidence interval (CI)=37.8?53.2%) and 18% of all women (95% CI=13.6?21.5%) with dementia were sexually active. The rate of sexual function problems was high across gender and cognitive groups (77%). Having sex primarily out of obligation was similar across cognitive groups for women (12%) and higher in men with dementia (17%) than other men (2?5%; P <.001). The majority of people were having sex less often than they would like. Few men (17%) or women (1%) with dementia talked with a doctor about sex. Conclusion Many home-dwelling men and women with dementia are sexually active. Although the rate of sexual function problems was uniformly high, people with lower cognitive function infrequently discussed sex with a physician.