The number of children residing in single-father families in the United States quadrupled as a proportion of children's living arrangements during the past few decades of the 20th century. Research on single fathers also increased and changed in nature. This article is a review of the research on single fathers and their families from the 1970s until recently, focusing on modifications in methodology and theoretical underpinnings. In general, research on single-father families evolved from qualitative studies focused on the well-being of single fathers to quantitative studies focusing on child outcomes and within-group variation among single fathers. Research also moved from descriptive studies to those testing gender and microstructural theories. This article also summarizes the main findings on single fathers and concludes with directions for future research.