To develop a model linking the processes and outcomes of workplace learning. We synthesised a model from grounded theory analysis of group discussions before and after experimental strengthening of medical students' workplace learning. The research was conducted within a problem-based clinical curriculum with little early workplace experience, involving 24 junior and 12 senior medical students. To reach their ultimate goal of helping patients, medical students must develop 2 qualities. One is practical competence; the other is a state of mind that includes confidence, motivation and a sense of professional identity. These 2 qualities reinforce one another. The core process of clinical workplace learning involves 'participation in practice', which evolves along a spectrum from passive observation to performance. Practitioners help students participate by being both supportive and challenging. The presentation of clear learning objectives and continuous periods of attachment that are as personal to the student(s) and practitioner(s) as possible promote workplace learning. The core condition for clinical workplace learning is 'supported participation', the various outcomes of which are mutually reinforcing and also reinforce students' ability to participate in further practice. This synthesis has 2 important implications for contemporary medical education: any reduction in medical students' participation in clinical practice that results from the patient safety agenda and expanded numbers of medical students is likely to have an adverse effect on learning, and the construct of 'self-directed learning', which our respondents too often found synonymous with 'lack of support', should be applied with very great caution to medical students' learning in clinical workplaces.