Inadequate midfacial and forebrain development may result from constitutional chromosome aberrations, gene defects and, possibly, from as yet unidentified terato-genetic agents. The spectrum of clinical manifestations ranges from cyclopia with grossly incomplete organogenesis of the forebrain to apparently minor deviation from normal midface morphogenesis presenting as hypotelorism or absence of the philtrum. Such minor facial dysmorphias may, however, be likewise accompanied by severe anomaly in brain development and function. We report six cases of holoprosencephaly defects in children without demonstrable chromosomal anomalies. The presenting clinical symptoms in these cases were anomalies of cranio-facial shape, hypotelorism; nasal and ocular malformations, as well as median clefts. Some cases presented additional defects in extra craniofacial regions. Two infants who survived for several hours showed evidence of forebrain defects on CT-scans. Three of the cases suggest autosomal-recessive inheritance with 25% recurrence risk on the basis of proven or highly probable parental consanguinity. The remaining, presumably sporadic cases carry a low empirical recurrence risk. Three of the six cases received direct or indirect hormone treatments during early pregnancy.