Busulfan or Misulban is considered by many the treatment of choice in chronic myeloid leukemia, for which it is used as a single agent. An interstitial fibrosing lung disease occurring after Busulfan was first described in 1961 and to date 56 cases have been published and are the object of this review. The clinical picture of this drug induced disease is well characterised. The disorder has an estimated incidence of 6% and begins gradually, marked by non-specific signs (dyspnoea, cough) and by an alteration in the clinical state, often severe, and is frequently accompanied by skin pigmentation. As a rule it occurs after prolonged treatment (on average 41 months, cumulative dose 2.900 mg). The respiratory function pattern is that of an interstitial fibrosis characterised by reduced volumes and hypoxaemia and hypocapnic respiratory failure. The radiology reveals interstitial and predominantly basal shadows. The histology is often obtained, either by lung biopsy or frequently at necropsy, because the prognosis is poor with an 84% mortality from respiratory failure. As for numerous interstitial pneumopathies, it poses questions as to the pathogenesis and early detection, problems which at present are imperfectly resolved.