This study conducted a preliminary test of two theories (general alienation and replacement) of support networks in relation to duration of homelessness. Nine hundred respondents experiencing homelessness were selected randomly from shelters and day centers and recruited from city streets. Information obtained from interviews included number and perceived reliability of supports—distinguishing between family supports, friend supports with homes, and friend supports without homes. Duration of homelessness was defined by shorter ( 12 months) versus longer (> 12 months) length of lifetime homelessness. Support for the general alienation theory included associations between longer-term homelessness and smaller family support networks and inability to count on family and friends. Support for the replacement theory included the lack of differences between the two groups in terms of number of friends and the association between longer-term homelessness and inability to count on friends. (Authors)