Objective: This study examined national patterns of outpatient service use by veterans from regions affected by Hurricane Katrina. MethodsAnalyses tracked use of general medical and mental/substance use services in September and October through December 2005 in New Orleans and Biloxi-Gulfport compared to a cohort receiving care during the same months in the previous 2 years. Results: In adjusted models, veterans from New Orleans and Biloxi-Gulfport were, respectively, 73% and 41% less likely in September 2005 to use any outpatient services as were cohorts from 2003–2004. Particularly in New Orleans, the relative decline in service use was substantially greater for specialty mental health and substance use services than for general medical services. Conclusions: Although many veterans were able to obtain care after Hurricane Katrina, there was a substantial disruption in delivery of Veterans Administration services, with disproportionate declines in mental health and substance use care.