Assessment of Prior Learning (APL) refers to a process where adults' prior learning, formal as well as informal, is assessed and acknowledged. In the first section of this paper, APL and current conceptions of validity in assessments and its evaluation are presented. It is argued that participants in the assessment are an important source of information for the validation of the assessment. In the following section participants' experiences from a particular APL scheme are evaluated using a questionnaire developed for that purpose. The questionnaire provides data on individuals' perceptions of the procedure and result of the APL scheme. The results are described, analysed and discussed from a validity perspective. Conclusions drawn from the results are that possible threats to validity can exist in the administration of APL procedures, as well as in consequences of APL. (Contains 3 tables.)