Case management-based interventions aimed at improving quality of care have the potential to narrow racial and ethnic disparities among people with chronic illnesses. The aim of this study was to assess the equity effects of assertive community treatment (ACT), an evidence-based case management intervention, among homeless adults with severe mental illness. <b>Methods:</b> This study used baseline, three-, and 12-month data for 6,829 black, Latino, and white adults who received ACT services through the ACCESS study (Access to Community Care and Effective Services and Support). Zero-inflated Poisson random regression models were used to estimate the adjusted probability of use of outpatient psychiatric services and, among service users, the intensity of use. Odds ratios and rate ratios (RRs) were computed to assess disparities at baseline and over time. <b>Results:</b> No disparities were found in probability of use at baseline or over time. Compared with white users, baseline intensity of use was lower for black users (RR=.89; 95% confidence interval [CI]=.83-.96) and Latino users (RR=.65; CI=.52-.81]). Intensity did not change over time for whites, but it did for black and Latino users. Intensity increased for blacks between baseline and three months (RR=1.11, CI=1.06-1.17]) and baseline and 12 months (RR=1.17, CI=1.11-1.22]). Intensity of use dropped for Latinos between baseline and three months (RR=.83, CI=.70-.98). <b>Conclusions:</b> Receipt of ACT was associated with a reduction in service use disparities for blacks but not for Latinos. Findings suggest that ACT's equity effects differ depending on race-ethnicity. (Psychiatric Services 62:598-604, 2011).