This paper discusses the extent, distribution, and consequences of socially isolated mothers. First, the author considers what are likely to be the negative effects of isolation on both the emotional and physical health of mothers, and the resulting implications of these effects for the primary prevention of a wide range of emotional and physical problems. Next, arguing that we do not know enough about social isolation beyond its possible effects on health, the author reviews data which have a bearing on the prevalence and distribution of social isolation in the population and how it affects mothers and through them their children on a day-to-day basis. Finally, the author discusses the implications of these findings for intervention and briefly describes the efforts in one particular neighborhood to reduce the isolation of mothers at home with their preschool children. Data reflecting the extent, distribution, and other characteristics of isolated mothers are included in tabular form. (Author/MP)