OBJECTIVES New health technologies are required to demonstrate clinical- and cost-effectiveness before being recommended by NICE for use in the National Health Service. A large proportion of submissions are rejected, at least in part, due to poor trial design or flaws in the presented clinical data. Published NICE guidance includes a comprehensive critique of submitted clinical evidence. Therefore, the flaws in clinical data leading to rejection by NICE were examined, as a means of providing guidance for future submissions. METHODS All single technology appraisals from January 2006 to May 2014 from NICE were included in the analysis. Multiple technology appraisals, resubmissions, vaccination programmes, and requests for advice were excluded. The recommendation and reasoning behind each decision were assessed, focusing on the critique of the clinical evidence. RESULTS