Aim: The present study sought to document client attendance norms at a multi-site outpatient alcohol and other drug (AOD) treatment service located in Auckland, New Zealand. Method: Service attendance data were retrospectively analysed for two client cohorts: consecutive admissions over the period 1 January 2001 to 31 March 2001 (n = 501) and a sub-sample of admissions who were entering the treatment service for the first time over the same period (n = 325). Data from the former cohort were analysed over a single episode of care. Data from the latter sample were analysed over a period of five calendar years (1 January 2001 to 31 March 2005). Results: Across a single episode of care, 73% of the respective client cohort exited treatment having attended four or fewer appointments. Furthermore, 61% of these clients exited treatment against clinical advice or prior to completing a scheduled treatment appointment. Only 15% of the 'new to treatment' sub-sample initiated a second episode of care during the next five calendar years and only 4% initiated a third. Conclusions: Patients attending a large outpatient AOD service in Auckland, New Zealand, typically attend few appointments and are unlikely to return for further treatment following discharge. These findings suggest outpatient AOD services should strive to impart the maximum benefit in the shortest possible time frame and/or increase client attendance duration.