This study assessed gains that New York State mental health and addiction outpatient clinics achieved in their capacity to provide integrated mental health and substance abuse services for persons with co-occurring disorders. The investigators used two Dual Diagnosis Capability (DDC) indices-one for Addiction Treatment (DDCAT) and one for Mental Health Treatment (DDCMHT)-to measure integration capability at baseline (n = 603) and at follow-up (n = 150), an average of 2 years post-baseline, during which time programs received technical assistance and implementation support. At baseline, the average program score was 2.68, below the "Capable" level (3.0 on a 5-point scale). At follow-up, the average score was 3.04, and the percent of programs rated Capable more than doubled (from 22 to 52%). Programs with lower baseline scores and those with more time to follow-up (2-3 years) had the greatest increases, but 12 to 18 months were sufficient to realize sizeable and significant improvements.