a pilot study of the mental workload of objective structured clinical examination examiners context mental workload is a concept used in many industries to investigate operator performance but it has only recently been used in the educational setting it has been suggested that excessive mental workload in assessors may impair the validity of objective structured clinical examination oscetype assessmentsobjectives this study aimed to establish the feasibility of measuring the mental workload of examiners during an osce assessment and to establish methodologies and baseline values to guide future study designmethods two previously validated methods of measuring mental workload the nasatask load index rating scale and use of a secondary task response to a prompt from a vibrotactile device were used to measure the workload of 10 subjects during a formative osce trainee anaesthetists n 24 working in an operating theatre were used as a control groupresults the mental workload of examiners exceeded that of controls on both measures although there was marked intersubject variability reliability between stations for individual examiners was robust 0922conclusions these data suggest that mental workload is excessive in osce examiners further studies are required to measure the effect of changes in assessment design and examiner training