['To ascertain the effects of baseline pain on depression outcomes in a collaborative care treatment trial of depression for older adults.', 'A secondary data analysis of 1,801 depressed older adults in the Improving Mood: Providing Access to Collaborative Treatment trial, comparing groups with no/low and high baseline pain using two pain interference variables. The primary outcome was a 50% reduction in depression score at 12 months. Analyses were performed separately for usual care and intervention groups, then examined for interactions.', 'In the treatment-as-usual group, there was no significant association of baseline pain status with depression outcomes. In the intervention group, higher pain interference was significantly associated with worse depression response: 48.9% of those with no/low pain interference achieved a depression response, compared with 37.4% of those with high pain (chi2 = 12.27, df = 1, p = 0.001). Arthritis pain interference showed a similar association (chi2 = 4.04, df = 1, p = 0.044). Controlling for sociodemographic and baseline characteristics did not diminish this association. A significant interaction effect on depression response was found between pain interference and the intervention, suggesting that higher pain differentially impairs depression response in collaborative care compared to usual care.'] Does pain limit the effectiveness of collaborative care for depression?