To define the major problems faced by pre-registration house officers, 328 critical incidents from 200 house officers and related staff were collected. Each incident was analysed and key words representing the main features were abstracted. These were then aggregated into eight broad categories; personal aspects, clinical skills, communication and relationships, problem-related, organization skills, education, dying patients, and administration. Further analysis of the incidents suggested a series of conclusions which include the need for effective supervision of the house officer with feedback on performance. An induction/orientation period is necessary; there is evidence that a proportion of house officers need additional experience of practical procedures; house officers often have difficulty in setting priorities and they have little experience, prior to qualification, of organizational skills; during the year they are very busy with little time off. Facilities and accommodation may be less than adequate. They perceive a lack of support from senior staff to help with personal problems and career guidance; they are conscious that communication skills are of great importance and would like additional help with this; there is little time for formal education during the year. The range of clinical material presented is enormous, however, and the challenge for medical education is to ensure that the opportunities for learning are not missed.