For 75 consecutive days, 54 Ss with rheumatoid arthritis supplied daily reports of their mood and joint pain. After aggregating daily reports, the relation between chronic mood and chronic pain remained statistically significant when controlling for neuroticism, depression, disease activity, disability, and characteristic responses to increasing pain. Findings of a path analysis suggest that (a) individuals higher in neuroticism experience more chronic distress regardless of their responses to pain, their pain intensity, and depressive symptomatology, and (b) the relation between neuroticism and chronic pain is mediated by the propensity of high-neuroticism individuals to catastrophize their pain. Within-subject analyses that controlled for autocorrelation and linear trends in the time series revealed that 40% of the Ss experienced significantly worse moods on more painful days. Although individuals higher in neuroticism reported more intense pain and more negative mood, their daily mood was less strongly linked to their daily pain.