l-P-Z)-Arabinofuranosylcytosine-5’-stearylphosphate (fosteabine) was administered orally to patients with myelodysplastic syndromes (MDS); refractory anemia with excess of blasts (RAEB), RAEB in transformation, acute leukemia derived from RAEB and chronic myelomonocytic leukemia, in an early phase II study in a multi-institutional study. Among 62 evaluable patients, 2 patients achieved a complete remission, 6 a good response and 8 partial response by daily oral administration of 100–200 mg of fosteabine. The overall response rate was 25.8%. The response rates were almost the same among the four subtypes of MDS. Responses were reached 2–23 weeks (median, 8 weeks) after the start of therapy and continued for 3–50 weeks (median, 10 weeks). Major side effects were myelosuppression and gastrointestinal toxicities. In spite of the disadvantages, such as unpredictable absorption, this newly developed orally administrable cytarabine analogue will be a useful drug in the treatment