According to previous animal research and psychological laboratory experiments in humans, plasma prolactin varies in relation to psychosocial stress. However, the findings in published studies are difficult to interpret. In some studies increased levels and, in other studies, decreased levels were observed. The present report summarizes findings from four different real-life stress studies that have had a longitudinal design. Findings indicate that change situations associated with passive coping are accompanied by increased plasma prolactin levels whereas change situations associated with active coping are associated with unchanged or even lowered levels. The regulation of plasma prolactin is part of a dopaminergic system. It is speculated that prolactin may be needed for preservation of vital functions during withdrawal.