In-training assessment (ITA), defined as multiple assessments of performance in the setting of day-to-day practice, is an invaluable tool in assessment programmes which aim to assess professional competence in a comprehensive and valid way. Research on clinical performance ratings, however, consistently shows weaknesses concerning accuracy, reliability and validity. Attempts to improve the psychometric characteristics of ITA focusing on standardisation and objectivity of measurement thus far result in limited improvement of ITA-practices. The aim of the paper is to demonstrate that the psychometric framework may limit more meaningful educational approaches to performance assessment, because it does not take into account key issues in the mechanics of the assessment process. Based on insights from other disciplines, we propose an approach to ITA that takes a constructivist, social-psychological perspective and integrates elements of theories of cognition, motivation and decision making. A central assumption in the proposed framework is that performance assessment is a judgment and decision making process, in which rating outcomes are influenced by interactions between individuals and the social context in which assessment occurs. The issues raised in the article and the proposed assessment framework bring forward a number of implications for current performance assessment practice. It is argued that focusing on the context of performance assessment may be more effective in improving ITA practices than focusing strictly on raters and rating instruments. Furthermore, the constructivist approach towards assessment has important implications for assessment procedures as well as the evaluation of assessment quality. Finally, it is argued that further research into performance assessment should contribute towards a better understanding of the factors that influence rating outcomes, such as rater motivation, assessment procedures and other contextual variables.