Long hours and other difficult working conditions are thought to affect the health of young doctors, but there has been little evidence to support these assertions. Data are presented from a class cohort of junior doctors in the U.K. showing the relationships between working conditions, health and performance. Long hours appear to have short-term consequences in terms of the doctors feeling unwell and reporting poor performance, as measured by the somatic and social dysfunction scales of the General Health Questionnaire, but there are no demonstrated long-term health consequences. Instead, a number of working conditions, number of emergency admissions, number of deaths on the ward and the number of minor menial tasks contribute to a perception of being overwhelmed, as revealed by factor analysis of the Attitudes to Work questionnaire. This factor correlates significantly with a range of long-term physical and mental health measures as well as measure of work performance.