This study examined the relationship between social support (Social Provisions Scale) and stress (Perceived Stress Scale) in a sample of male firefighters in a midwestern community (N=53). The authors assessed 5 types of perceived support from 2 sources: peer firefighters and supervisors. Results indicate that reassurance of worth and social integration support from supervisors had the strongest negative association with stress. The study critically examined the "unidirectional linear" assumption that a unit increase in support corresponds to a unit increase in adjustment throughout the full range of support scores. Reassurance of worth support from peers exhibited a curvilinear pattern of threshold effects. For individuals with the lowest levels of support, there was a strong negative association between perceived support and stress, but for firefighters above the median, the association was not significant.