The increase in the number of persons living alone and the patterns of residentia1 mobility among one-person households can only be understood in light of the transitions between one-person and multi-person households. The likelihood of a change in dwelling or household composition varies among one-person households, most obviously with the age of the person living alone. This paper presents exploratory research on one-person households, the processes leading to their formation and dis-solution and the residential mobility associated with such households. The analysis is based on panel data collected over a two year time period in the United States and the Federal Republic of Germany.