SummaryFrom 1954 to 1963, 113 patients suffering from pancytopenia were studied at the Medical Institute of the University of Liège.The etiological inquiry was fruitless in 40 % of the cases; there were considered as idiopathic forms of pancytopenia. Among the etiological factors discovered in the other patients (60 % of the cases)( there were, in descending order of frequency, antimitotics, malignant hematological disorders, infections and endocrine disorders.In most of the cases, the three blood series were affected. The platelets appeared particularly sensitive. On the other hand, the granulocytes were somewhat more resistant.The distribution according to age and sex was identical for both idiopathic and symptomatic forms. The prognosis seems independant of the cellularity of the bone marrow smear. In any case, it is unfavorable (85 out of 113 patients deceased). The symptomatic forms are more evolutive.Accidental bleeding with cerebro-meningeal localization is the most frequent cause of death.None of the therapeutics practised gave formal proof of its efficacity, aside from etiological treatments applied to two cases associated with thyroid disorders. These results may be compared with those found in recent literature.