Comparing heterosexual cohabitating couples with corresponding married couples ( 'matching' ) between 20 and 40 years old, on some social and psychological characteristics, in the Netherlands and in the USA. Duration of relationship / separate or joint responsibility for lodging, finances / approval by others of this kind of relationship / having made formal legal provisions in cases of separation or death / planning children / reasons for living together / reasons for eventual marriage / circumstances under which partner could be left / expectations before starting to live together / statements regarding a variety of issues / relation to parents. Background variables: basic characteristics/ household characteristics/ characteristics of parental family/household/ occupation/employment/ income/capital assets/ education/ religion