A large body of research has linked social support to health, but there are fewer studies that have focused on factors that influence the level of social support available and/or perceived by employees in different organisations. This cross-sectional study therefore investigated the relationship between on the one hand, organisational, individual and socio-demographic factors and on the other, the level of social support at the workplace, i.e., the degree of supervisor support and a supportive work atmosphere. Organisational variables (job demands, job control, job content), individual (self-esteem, mistrust) and socio-demographic variables (type of employer, occupational position, age, gender and educational level) were used as independent variables in the analyses. The sample consisted of 16,144 individuals at a variety of different organisations in Sweden, who had responded to a questionnaire covering different psychosocial and psychological stress factors ("the Stress Profile"). Multiple hierarchical regression analyses were performed separately for each of the two dependent variables, which yielded almost identical results, and indicated that organisational determinants, particularly perceived job control, had the largest impact on the degree of social support.