The patient was a 47-year-old woman with a painful ulcer that had appeared on the right 5th toe two weeks before she visited our hospital. Histopathological examination showed that thrombi were present in small blood vessels in the dermis and pancytosis was detected in a blood test, suggesting polycythemia-associated ulceration of the toe. Essential thrombocythemia was diagnosed based on bone marrow puncture and chromosomal test findings. Platelet count and the ulcer were improved by oral hydroxyurea.