Despite midlife adults accounting for a substantial and growing segment of the population, few large-scale studies have investigated factors which distinguish highly satisfying relationships from less satisfying ones in midlife. In a subsample of partnered 40-59-year-old Canadians (705 men, 743 women), relationship characteristics, sexual activity and communication, and health were investigated individually and simultaneously as predictors of high emotional and sexual satisfaction. Though the vast majority of participants reported being at least somewhat satisfied in their current relationship, less than half reported high satisfaction. For men and women, high emotional and sexual satisfactions were strongly linked. Logistic regressions indicated that longer relationships, dating relationships, and greater subjective overall health predicted high emotional satisfaction for men, whereas older age, married or cohabiting relationships, and frequent sexual communication predicted high emotional satisfaction for women. All types of sexual activities (minus penile-anal intercourse) were bivariately related to high emotional and sexual satisfaction. More frequent partnered sexual activity predicted high emotional and sexual satisfaction for men and women in regression analyses. More frequent sexual communication predicted high emotional satisfaction for women and high sexual satisfaction for both men and women. Newer relationships were more sexually satisfying for men. Postmenopausal women were less likely to be highly sexually satisfied. Findings suggest that physical health conditions are not generally related to high levels of satisfaction in midlife couples and that frequently discussing sex and engaging in (any) sexual activity with a partner are key components of highly satisfying relationships. [ABSTRACT FROM AUTHOR]