A group of homeless people living in the streets is described with the purpose of gaining the knowledge necessary to prevent development of homelessness and establishing programmes for the homeless. Out-reach work in the streets and cooperation with private and religious organisations was conducted during a two-year period and 59 homeless persons were interviewed. Fifteen were women and 44 were men. Upbringing, social conditions, daily living, physical and mental health and contact with health services, social security and private organisations were highlighted in a structured and semistructured interview. Compared with the background population the homeless had much more frequently childhood experience of parents' divorce or death of one of the parents. The women were significantly older than the men and the majority of the women were suffering from schizophrenia and had very little contact with network and public services. The majority of the men were abusing alcohol or drugs, many had had a troublesome childhood with stays in institutions. Many had had many contacts with different social institutions and a criminal record. Among the homeless in the streets of Copenhagen, the prevalence of mental illness, especially schizophrenia, is high. It is recommended that homelessness among the mentally ill is prevented by a special effort directed towards the patient group at risk of becoming homeless and through establishing different housing facilities with varying degrees of professional support. Out-reach work towards the homeless mentally ill should be carried out with the purpose of establishing contact with psychiatric services and securing the possibility of compulsory admission.