The Network for the Improvement of Addiction Treatment (NIATx) teaches participating treatment centers to use process improvement strategies. A cross-site evaluation monitored impacts on days between first contact and first treatment and percent of patients who started treatment and completed two, three and four units of care (i.e., one outpatient session, 1 day of intensive outpatient care, and 1 week of residential treatment). The analysis included 13 agencies that began participation in August 2003, submitted 10-15 months of data, and attempted improvements in outpatient (n=7), intensive outpatient (n=4) or residential treatment services (n=4) (two agencies provided data for two levels of care). Days to treatment declined 37% (from 19.6 to 12.4 days) across levels of care; the change was significant overall and for outpatient and intensive outpatient services. Significant overall improvement in retention in care was observed for the second unit of care (72-85%; 18% increase) and the third unit of care (62-73%; 17% increase); when level of care was assessed, a significant gain was found only for intensive outpatient services. Small incremental changes in treatment processes can lead to significant reductions in days to treatment and consistent gains in retention.