The United States is known as a mobile society and recently Sweden has also seen higher rates of mobility. A study was conducted to examine how local residential mobility affects the lives of families in Sweden and in black and white communities in the United States, and to investigate how moving affects social networks. Interviews were conducted with mothers in 413 urban families with a preschool child and follow-up interviews were conducted with 326 of the mothers 3 years later. The United States sample consisted of 53 black and 162 white families in 18 neighborhoods near Syracuse, New York. The Swedish sample consisted of 111 families in Gothenburg and Stockholm. Subjects answered questions about neighborhoods and moves they had made, completed social network lists during the initial interview, and revised lists at the follow-up interview. The results indicated that residential moves were common in all three cultural groups--over one-third of the subjects moved at least once during the 3 years and one-fifth of their network ties were broken. Yet moving and breaking network ties were not closely linked. The effects of different policy environments could be seen in types of moves made by families in each culture. When it came to predicting network change, however, personal characteristics and social preferences were more powerful than macro-social variables. (NB)