This paper draws primarily on an ESRC-TLRP longitudinal study of early career professional learning, which focused on the first three years of employment of newly qualified nurses, graduate engineers seeking chartered status and trainee chartered accountants. The first section introduces the theoretical and methodological base provided by previous projects, then proceeds to explore an epistemology of practice, using three dimensions: (1) four key elements of practice--situational assessment, decision-making, actions and meta-cognitive monitoring; (2) the mode of cognition and its dependence on time and prior learning; and (3) the context, its influence on mode of cognition and its affordances for learning. The central section presents the project's findings on modes of learning through a new framework, which divides learning processes according to whether the object is perceived to be learning or working, then adds a list of shorter learning activities used within both types of process, including various types of mediating artifact. The final section summarises the project's findings on factors affecting learning, then draws practical conclusions from the project's work. (Contains 2 tables and 1 figure.)