We set out to identify clinical or analytical variables that might predict the response to splenectomy in patients with chronic idiopathic thrombocytopenic purpura (ITP). We retrospectively examined 138 mostly adult patients with chronic ITP, treated with splenectomy. Information was compiled from five Public Health Hospitals from a questionnaire and chart review. Sixty-one potentially prognostic variables were analysed by univariate and multivariate statistical methods. After multivariate analysis, age (relative risk = 1.02; CI 1-1.03) and a severity of the bleeding diathesis (relative risk = 1.6; CI 1.13-2.22) were independent prognostic factors for a sustained response to splenectomy. An independent analysis of the postsplenectomy counts showed that an early (days 1-3) thrombocyte count exceeding 156 x 10(9)/l cells increases the likelihood of a permanent unmaintained response. Our data indicate that the response to splenectomy in patients with chronic ITP cannot be adequately predicted on the basis of pre-splenectomy clinical or analytical variables.