BACKGROUND The complications of varicella are one of the arguments in favor of universal vaccination programs in children. OBJECTIVE To describe the complications of varicella requiring hospital admission in a well-defined population (Gipuzkoa, Spain) and to compare the incidence of hospitalization with that reported in other series. METHODS Observational, retrospective, multicenter study of admissions for varicella. The medical histories codified as varicella (minimum data set, CIE-0, codes 952.0-052.9) from 1 January 1993 to 31 December 2002 were reviewed. Calculation of hospitalization rates was based on emergency department visits and population data. The pediatric population of Gipuzkoa seeking medical attention at one of the four Basque Country Health Service hospitals in the area: Hondarribia, Mendaro, San Sebastian and Zumarraga. The mean coverage in Gipuzkoa is 54,999 children aged less than 15 years/year. All the children aged 0-15 years old admitted for more than 24 h with a discharge diagnosis of varicella complications. The variables studied are: age, gender, personal history, varicella immunization, immune status, fever, chest X-ray, complementary investigations, length of hospital stay, treatment, discharge diagnosis, clinical course, complications and sequelae at discharge. RESULTS Seventy-one children were hospitalized. None had been vaccinated against the varicella-zoster virus. Eighty percent were aged less than 5 years and three were immunocompromised. Fifty-six percent had bacterial superinfection and invasive forms were found in seven patients. The mean length of admission was 6.5 days +/- 5.1. No deaths or sequelae were reported. CONCLUSIONS The annual incidence rate of admissions longer than 24 hours due to varicella complications was 12.9 cases per 100,000 children aged less than 15 years, representing 0.31% of all annual admissions in this age group.