Hydroxyurea (HU) is a drug frequently used in the treatment of chronic myeloproliferative neoplasms. The most common side effects of this drug are pancytopenia, digestive and skin disorders. Respiratory complications are rare and there are less than 20 cases described, only 5 of which underwent an anatomopathological study. We present the case of a patient with chronic myeloproliferative neoplasm who developed interstitial pneumonitis probably due to HU according to histological study.