Juvenile myelomonocytic leukemia (JMML) is a myeloproliferative/myelodysplastic disorder associated with mutations in the Ras-Raf-MEK-ERK-signaling pathway. B-Raf plays a central role in this pathway. In 65 screened JMML patients we identified no BRAF mutations and we conclude that this gene is unlikely to play a role in the pathogenesis of JMML.