This paper promotes research methods specific to men, the new focus of fertility and family planning studies (especially in sub-Saharan Africa). I propose a novel marriage categorization based on married men’s intentions to take another wife. The three marriage groups are currently monogamous men who intend to remain so, currently monogamous men who intend to become polygynous, and currently polygynous men. The first analysis demonstrates that typical marriage analyses may misclassify men who intend to become polygynous. Applications of the marriage trichotomy illustrate that men with varying marital intentions have differing desires regarding fertility and family planning.