Both, homelessness and loneliness are quite pervasive in North America. This study compared the causes of the loneliness experienced by the homeless to that of the general population. Two hundred and sixty six homeless and five hundred and ninety five men and women from the general population answered a 30 item yes/no questionnaire. The causes of loneliness were composed of the following five factors: Personal inadequacy, Developmental deficits, Unfulfilling intimate relationships, Relocation/significant separations, and Social marginality. The present results indicated that the causes of homeless loneliness are significantly different from those of the general population.