With consideration given to the actuality of the problem of drug affections of hemopoiesis, the authors carried out clinical-morphological studies on drug-induced bone marrow insufficiency. The study covers 203 patients, treated at the Hematological Clinic of Higher Medical Institute-Pleven during the period 1976-1984. Drug etiological factors (other than cytostatics) were established in 23.2% of the patients with bone marrow hypoplasias and in 83.33% of those with leuko- and granulocytopenia, the non-narcotic analgesics responsible for the greatest share. Some clinical and morphological characteristics of the various clinical-hematological forms of the drug-induced bone marrow insufficiency are described. The necessity of purposeful hematological control is stressed on in case of long-term administration of drugs with potential hematotoxicity.