This study examined the use of prescription drugs among a sample of frequent injecting drug users (IDUs), frequent methamphetamine users, and frequent ecstasy users and found that pharmaceutical morphine was the principal opioid used by IDUs. Other findings include: injection of methadone by IDUs and methamphetamine users was common; more IDUs had a prescription to use morphine in 2008 than in 2009; more IDUs used oxycodone in 2009 compared to 2008, while prescription use of oxycodone by IDUs was low; and all three groups of drug users were involved in the use of methylphenidate and benzodiazepines. The purpose of this study was to determine the rate of pharmaceutical and prescription drug use among three different groups of drug users in New Zealand. Data for the study were obtained from 4 years of findings from the Illicit Drug Monitoring System (IDMS). The IDMS interviews 300 frequent drug users each year in 3 main urban centers in New Zealand and collects data on the demographics and rates of drug use among three distinct groups of users - frequent IDUs, frequent ecstasy users, and frequent methamphetamine users. Analysis of the data found that rates and type of pharmaceutical drug use varied among all three groups of frequent illegal drug users. Implications for control strategies for use with frequent illegal drug users are discussed. Tables and references