Abstract Objective To investigate the challenges experienced by pharmacists in delivering supplementary prescribing (SP) services, to explore their perceptions of benefits of SP and to obtain feedback on both SP training and implementation. Method A postal questionnaire focusing on prescribing training, early experiences of prescribing and general demographics was sent in September to November 2005 to all SP pharmacists (n = 488) in Great Britain after excluding a pilot sample (n = 30). The biggest benefits and challenges of SP, and reasons for not practising SP, were identified. Responses to a general open question were content analysed for major themes. Key findings A total of 401 responses (82.2%) was received; 195 (48.6%) had started practising SP of which 154 (79%) had written at least one prescription. This paper focuses primarily on perceived benefits and challenges to the implementation of SP, and the responses to the open question. Better patient management (n = 58; 29.7%) was identified as the main benefit of SP and inadequate funding (n = 27; 13.8%) as the biggest challenge in delivering SP service. The main reasons for not commencing SP were: no organisational recognition of SP (n = 37; 18%); lack of funding (n = 33; 16%); non-availability of prescription pads (n = 22; 10.7%), and change of jobs (n = 18; 8.7%). The comments to the open question (n = 145; 36.2%) were regarding: SP training; perceived benefits of SP; and barriers to SP. Respondents highlighted the need for greater emphasis on clinical skills development as part of the SP course. Conclusion Despite optimism among SP pharmacists, the need for support in terms of infrastructure and integration into the healthcare team has been identified. Our findings also inform the need for modifications in the structure, content and delivery of the prescribing course for pharmacists. Greater publicity of pharmacists' roles in medication management, support from the medical profession and healthcare organisations, and high standards by early practitioners are warranted for the success of SP by pharmacists.