STUDY OBJECTIVE: We sought to describe the spectrum of illness and number of patients seen by pediatric residents rotating through a pediatric ED. METHODS: Our study was set in the ED of a 200-bed referral children's hospital providing services exclusive of major trauma. We conducted a retrospective review of the database of all visits to the ED between July 1992 and June 1995. Our subjects were 19 pediatric residents who started residency in July 1992 and ended residency in June 1995. Ninety-one other pediatric residents completed individual ED rotations during the same period. RESULTS: The study ED had 70,129 visits between July 1, 1992, and June 30, 1995. The study residents saw a median of 467 patients per resident (range, 290 to 604) during their 3-year residencies. The range of patients seen per resident for the diagnosis of asthma was 35 to 86, that for otitis media was 16 to 110, and that for fever or sepsis was 17 to 62. Similarly large ranges were seen for other diagnoses evaluated and procedures performed by residents. The proportions of the study residents who never saw a case of pyloric stenosis, intussusception, or diabetic ketoacidosis in the ED were 37%, 32%, and 32%, respectively. CONCLUSION: The number and type of patients seen by individual residents in this study showed significant variation. Many illnesses were not seen frequently enough for every resident to develop competence solely on the basis of clinical experience during ED rotations. A computerized, easily accessible ED database can be used to track the experience of individual residents or groups of residents. Such tracking would allow residents and program directors to identify areas that may require alternate educational strategies and would also document the residents' experience for future credentialing.