This study examined the effects of anxiety and depression on pain in women with rheumatoid arthritis (RA; n=82) or osteoarthritis (OA; n=88). Anxiety and depression symptoms were assessed at the beginning of the study. Arthritis pain, interpersonal stress, negative affect, and positive affect were assessed weekly for 11 consecutive weeks. Multilevel analyses were conducted to investigate direct, indirect, and interactive effects of anxiety and depression on weekly changes in pain. When entered separately into the prediction equations, anxiety and depression were both related to elevations in current and next week pain, although the effects were nearly twice as large for anxiety. In addition, both anxiety and depression were indirectly related to current pain through negative and positive affect and depression interacted with stress to predict current pain in the RA group. When entered together into the prediction equations, anxiety alone was still related to elevations in current and next week pain. In addition, anxiety alone was indirectly related to current pain through negative affect and depression alone was indirectly related to current pain through positive affect. These results highlight the need for careful study of the differential effects of anxiety and depression and treatments that target their unique mechanisms.