This article examines the moderating effects of the Type A behaviour pattern on the relationship between paced work and psychological (mood) disturbance. The study was part of a broader survey investigation seeking to characterize job stress and health relationships among postal workers engaged in machine-paced letter-sorting operations. Data from 2803 paced letter sorters and 2715 non-paced Postal Service employees were analysed in a behaviour pattern × pacing × sex (2 times 2 × 2) design. Paced work was found to have a significant effect on mood state. However, no evidence of a Type A moderating effect was found. Results of the study for males but not females were consistent with Sales' (1969) theory that the Type A person possesses personality traits that predispose self-selection into stressful jobs. It was suggested that future studies of the relationships between pacing and the Type A pattern include multiple measures of the behaviour predisposition.