SUMMARY INTRODUCTION.Burnout syndrome which is prevalent among oncologists is characterized by three aspects: emotional exhaustion, depersonalization and low personal accomplishment. The purpose was to evaluate prevalence of the burnout syndrome among Brazilian medical oncologists and the variables that correlate with its presence. METHODS. A survey was conducted with members of the Brazilian Society of Medical Oncology (SBOC) who received three questionnaires (general, Maslach burnout questionnaire and an opinion survey) mailed to all 458 members. RESULTS. Response rate was of 22.3%. According to the criteria proposed by Grunfeld, which consider burnout present when at least one of the aspects is severely abnormal, prevalence of this syndrome was 68.6% (95% confidence interval, CI: 58.68% to 77.45%). By multivariate analysis having a hobby/physical activity, a religious affiliation, older age, living with a companion and rating vacation time as sufficient were correlated significantly and independently with burnout syndrome. CONCLUSIONS. The burnout syndrome is prevalent among Brazilian oncologists. Oncologists having sufficient personal and social resources to engage in a hobby, physical activity, have enough vacation time and religious activities are at lower risk of developing burnout.