Conceptualization and formulation of a theory about loneliness.Feelings of loneliness / contacts at work / conditions at work / job satisfaction / housing situation / contacts with the neighbours and in neighbourhood / social participation in organizations / contacts with six persons r is most intimate with / intensity of loneliness / self-rating of loneliness / time dimension / emotional aspects / missing contacts / interviewer's rating of loneliness of respondent.Background variables: basic characteristics / residence / housing situation / household characteristics / occupation/employment / education / politics / religion/ organizational membership