Twenty-four women out of 7,875 pregnant women who enrolled in a prenatal screening program showed extremely low levels of unconjugated estriol (< 0.15 MOM). In 19 cases, intrauterine fetal death was reported. In 1 case anencephalus was detected. In the remaining 4 cases apparently normal healthy babies (1 female and 3 males) were born following uneventful pregnancies. Physical examination of the 3 boys at 4–6 weeks revealed mild ichthyosis compatible with the X-linked type. Two of them had a positive family history of X-linked ichthyosis. The examination of the girl did not reveal any significant findings. In both cases in which amniocentesis was performed, low levels of steroid sulfatase and arylsulfatase C were found. The prevalence of X-linked ichthyosis in this study is higher than previously reported, i.e. 1:1,300 males. Our results suggest that the prenatal screening program for neural tube defects and for Down’s syndrome is useful for the prenatal detection of X-linked ichthyosis as well. These results are in accordance with two recent reports. The implications regarding genetic counselling are discus