Presented for vocational counselors is an overview of mental retardation, including the definition, and etiology. Described are the prenatal factors of heredity (including familial retardation and cranial anomalies), infections (including syphilis and encephalitis), radiation, blood group incompatibility, and unknown or variable etiological factors (including cretinism and mongolism). Prenatal causes (anoxia and vascular injuries), and postnatal influences (cerebral trauma and poisoning) are discussed. Preventive measures and research are described, followed by course requirements for a rehabilitation counseling degree. (CL)