AIMS: To explore service provision and the range of problems that New South Wales (NSW) and Victoria (VIC) community pharmacists providing opioid substitution treatment (OST) have experienced with clients and prescribers. DESIGN: ross-sectional postal survey. SETTING: All community pharmacies providing OST in NSW (n = 593) and VIC (n = 393), Australia. PARTICIPANTS: Completed questionnaires were received from 669 pharmacists (68% response rate). MEASUREMENTS: The questionnaire addressed pharmacy characteristics, recent problems experienced with clients including refusal to dose, provision of credit for dispensing fees, termination of treatment, responses of pharmacists to problems experienced with clients, as well as problems experienced with OST prescribers. FINDINGS: In the preceding month, 41% of pharmacists had refused to dose a client for any reason, due most commonly to expired prescriptions (29%), or > or issed doses (23%). Terminating a client's treatment in the past month was reported among 14% of respondents, due most commonly to inappropriate behaviour and missed doses. Treatment termination was reported by a significantly higher proportion of pharmacists in VIC (P < 0.001). Treatment termination in last month was predicted having more clients (P < 0.001), the provision of buprenorphine treatment (P = 0.008), having a separate dosing area (P = 0.021), and being a female pharmacist (P = 0.013). Past month refusal to dose was predicted by the pharmacy being in VIC (P < 0.001) and having more clients (P < 0.001). Problems experienced most commonly in the past month with prescribers were difficulty contacting prescriber (21%) and provision of takeaway doses to clients considered unstable by the pharmacist (19%) (higher in VIC: both P < 0.001). CONCLUSIONS: This study highlights the range of problems experienced by community pharmacists in the delivery of OST and the consequences for people in treatment. Particular attention should be focused upon considering number of clients per pharmacy and improving professional communication between pharmacists and prescribers.