Immune thrombocytopenia (ITP) has a favorable prognosis in children. Only a small number of children go on to develop chronic ITP. However, at the time of diagnosis, it is not possible to predict the course of the disease. In order to determine prognostic factors that could predict the disease course at diagnosis, we retrospectively evaluated various clinical variables in 103 pediatric patients with newly diagnosed ITP at our institution from 1995 to 2001. Sixty-eight (66%) patients had a mean platelet volume (MPV) of <8 fL on admission. Of 72 patients who had a follow-up period of at least 6 months, 54 (75%) achieved a durable remission within 6 months and 18 (25%) developed chronic ITP. In univariate analysis, a low admission MPV (<8), history of viral prodrome, and a low admission platelet count (<10×109/L) predicted for a favorable outcome. Age and sex did not correlate with remission. In multivariate analysis, a low admission MPV and a history of a viral prodrome were the only independent factors correlated with a durable CR. The adjusted odds ratio for achieving a durable remission was 8.9 (95% CI: 1.54–51.8) for history of a viral prodrome and 14 (95% CI: 2.52–83.3) for low admission MPV value. In conclusion, our study showed that a majority of the children with newly diagnosed ITP presented with a low MPV value. A history of viral illness and a low admission MPV were found to be independent prognostic variables that predicted for the achievement of a durable CR in childhood ITP. Am. J. Hematol. 77:358–362, 2004. © 2004 Wiley-Liss, Inc.