Background: Following the MPharm degree, the pre-registration training year is a critical time where the values, attitudes and behaviours of qualified pharmacists are inculcated. Given the paucity of research, a programme of work was undertaken to explore the process of professional socialisation and development of professionalism in trainees during the pre-registration year.Method: The programme of work, the first of its kind in pharmacy, explored the process of professional socialisation and development of professionalism in trainees prospectively during the 2011/12 pre-registration year. A purposive sample of 20 pre-registration trainee-tutor pairs - 14 from community and 6 from hospital pharmacy - were recruited across North West England. Semi-structured interviews and behavioural professionalism questionnaires were used longitudinally in four rounds of data collection during the training year and with newly qualified pharmacists (NQPs; formerly trainees). A cross-sectional survey was administered to 1706 trainees towards the end of the training year to examine areas explored in the longitudinal study, including behavioural professionalism, supervision and 'patient mattering'. Interviews were analysed thematically using template and framework analyses, and the critical incident technique. Quantitative data was analysed using descriptive and multivariate analyses.Results: Findings demonstrated that many of trainees' attitudes and values appeared to be fostered during their upbringing and were further shaped by the MPharm degree, laying out professional expectations for pharmacists. At the beginning of training, sector differences were apparent with more formalised inductions in place in hospital than community pharmacies, particularly independents. Previous pharmacy work experience, which all 20 trainees had undertaken during MPharm studies, facilitated the transition into training. Early on in the year, as trainees familiarised themselves with the organisation and working processes they were often supported by pharmacy technicians and other support staff and trainees worked effectively and in a professional manner with them throughout training. The application of clinical knowledge acquired from the MPharm degree was challenging, as recognised by trainees and tutors. With continued practice experience and increased responsibility and patient contact, abilities in applying clinical knowledge and communicating with patients improved, as did trainees' confidence. Longitudinal ratings of behavioural professionalism increased significantly during training, as assessed by trainees and their tutors, and this was confirmed in the analysis of a representative sample of 347 trainees that were surveyed (response rate = 24.2%). Survey findings showed how elements of behavioural professionalism such as communication skills were more prone to development compared to, for example, appearance and interpersonal skills. Perceptions of supervision received during the training year were generally positive. The pre-registration tutor was a key source of support, as well as role model, throughout the year, particularly in community pharmacy. Hospital tutors had a more distant relationship with their trainees and relied on other pharmacists to supervise their trainees. Tutors were often considered to have the largest impact on the development of professionalism in trainees, particularly in community. When considering aspects of their supervision, hospital trainees rated their tutors significantly higher than those in community in 'articulation' and 'exploration', relating to asking trainees for rationale of actions and encouraging them to pursue learning goals, respectively. Differences between training sites, such as the pharmacy services being delivered and patient mix, were found as were trainees' beliefs that they mattered to patients: community trainees believed they mattered more (e.g. were more helpful) to their patients than hospital trainees.Conclusions: The multiple methods employed in this programme of work revealed experiences trainees faced and contributing factors associated with their professional socialisation and development of professionalism. The findings led to recommendations for pharmacy education and training including: integrating university-based and work-based learning more closely, ensuring consistency in training experiences in different settings and sectors, improving training and support for staff involved in training and setting explicit standards relating to elements of professionalism. These are considered in the context of anticipated changes to the MPharm into a more integrated 5-year degree programme.