The purpose of this paper is to review the social science research on marital dissolution and discuss its implications for family law reform. Numerous studies have found that compared with married persons, divorced persons tend to have lower levels of psychological well-being, lower happiness, and poorer self concepts. They have more health problems, a greater risk of mortality, a lower standard of living, more economic hardship, and are more likely to live in poverty. Social scientists offer two explanations for these differences, selection and stress. The selection explanation suggests that poorly functioning individuals have a high risk of divorce. Thus, characteristics that existed before the divorce produce the low levels of well-being. The stress explanation is that the process of divorce lowers people's well-being. Recent research which controls for pre-divorce characteristics lends support to the stress explanation. Although some of the differences are due to selection, divorce has an independent impact on well-being net of selection. Findings are consistent in showing that compared with children raised with continuously married parents, children of divorced parents score lower on a variety of measures of well-being. They have more depression, more psychological problems, poorer self concepts, poorer grades, more delinquency, more physical health problems, and are more likely to live in poverty. As teenagers, they tend to have sexual relations earlier and are more likely to get pregnant. As adults, children of divorce tend to achieve less education and are more likely to divorce themselves. However, divorce may be beneficial for children in high-conflict marriages. Again, social scientists have two interpretations for these differences, selection and stress. The selection interpretation suggests that negative outcomes are due to factors other than marital disruption, such as parents' personalities, inept parenting, pre-divorce marital conflict, or genetic influence. Research published during the nineties is consistent with the stress explanation; after controlling for pre-divorce characteristics, divorce is associated with increased problems among children. The mechanisms through which divorce affects children include diminished parenting, interference with parent-child relationships, conflict between former spouses, a decrease in emotional support, economic hardship, and an increase in other stressful life events. Social science research indicates that marriage is not just like other relationships and that there are tremendous private and public costs to our high divorce rates. The private costs affect the physical, psychological, emotional, and economic well-being of millions of adults and children. The public costs include strain on the health care system, increased welfare costs, higher crime rates, lower high school graduation rates, and greater criminal justice expenditures. These are real social costs that should be taken into account as we contemplate family law reform. These findings have implications that for the direction of family law reform. Most important is a recognition that marriage is a unique institution which provides many public and private benefits, while family dissolution produces tremendous public and private costs.