A tendency to manage anger via direct expression (anger-out) is increasingly recognized as influencing responses to pain. Elevated trait anger-out is associated with increased responsiveness to acute experimental and clinical pain stimuli, and is generally related to elevated chronic pain intensity in individuals with diverse pain conditions. Possible mechanisms for these links are explored, including negative affect, psychodynamics, central adipose tissue, symptom specific muscle reactivity, endogenous opioid dysfunction, and genetics. The opioid dysfunction hypothesis has some experimental support, and simultaneously can account for anger-out's effects on both acute and chronic pain. Factors which may moderate the anger-out/pain link are described, including narcotic use, gender, and genetic polymorphisms. Pain exacerbating effects of trait anger-out are contrasted with the apparent pain inhibitory effects of behavioral anger expression exhibited in anger-provoking contexts. Conceptual issues related to the state versus trait effects of expressive anger regulation are discussed.