Behavioral manifestations of pain, distress, and suffering have been characterized as pain behaviors. Although acquisition and maintenance of pain behaviors have been considered to occur through reinforcement contingencies, empirical evidence suggests that pain behavior is better understood as a multidimensional entity. The present study was designed to evaluate the contributions of physical, operant, cognitive, and affective factors to individual differences in pain behaviors. A total of 63 chronic pain patients diagnosed with the disorder fibromyalgia underwent medical, physical, and psychological evaluations. Hierarchical regression analyses revealed that the physical, cognitive, and affective factors, but not operant factors, were significantly related to observed pain behaviors. The set of all factors accounted for 53% of the variance in observed pain behavior. The results in this study suggest that pain behaviors should be conceptualized as behavioral manifestation of pain based on a complex interaction of various psychological and physical factors.