The sera of 3522 women who attended an antenatal clinic in Birmingham. England were tested anonymously for antibodies against HTLV-1. Samples from 5 women (0·14%) were positive, one serum showed indeterminate reactivity. Two of the women (0·06%) were born in the West Indies (of Afro-Caribbean ethnic origin), one (0·03%) in Africa (of African ethnic origin), and three (0·09%) were white Caucasian women born in the UK. Thus, HTLV-1 infection in pregnant women in the UK, though comparatively rare, is not negligible. As transmission of HTLV-1 to the newborn via breast milk has been observed and as seropositive mothers can be advised to refrain from breastfeeding or to treat their milk, the question of routine screening for HTLV-1 infection during antenatal care is discussed.