Aims and objectives. This study was designed to assess the training needs of health care support workers. In the past, opinions on the topic have been varied, but were rarely based on empirical evidence. Design and methods. The study was designed as a self-report questionnaire survey of health care support workers and their managers in six units in health and social care, using as its basis 32 descriptors from the NHS Knowledge and Skills Framework, levels 1 and 2. The achieved sample was 117, giving a 77% response rate. Results. Thirty-five per cent of respondents thought that health care support workers were 'unable' to perform six or more of the 32 descriptors used, whilst on the criterion of being 'less than able', the figure was 64%. Support workers and their managers agreed closely (rho ¼ 0Æ8) on where the difficulties lay in achieving Knowledge and Skills Framework competencies. Those difficulties lay particularly in two areas: (1) biomedical/physiological knowledge and (2) data-handling. Conclusions. We concluded that the numbers in need of training were substantial and the areas of need were the two identified above. Relevance to clinical practice. The main implications for clinical practice are that (a) for those who supervise or mentor health care support workers, there should be a greater concentration on the more scientific areas of expertise and (b) a similar emphasis is needed for those who train mentors or supervisors. These implications will become more important over time as scientific knowledge about medicine and health care increases.