We have been following up the biological and mental development of chi
ldren exposed prenatally to polychlorinated biphenyls and their contam
inants(Yucheng children). When we started this 12-year follow-up study
in August 1985, 118 Yucheng children we assigned a non-exposed child
matched by sex, age, locality of residence, mother's age, socio-econom
ic status of the family. This article reports the cognitive aspect of
the development of Yucheng children as compared to their matched contr
ols. A consistent tendency which indicates that Yucheng children score
lower in each kind of measurement tool at each age level has been obs
erved. This seems to imply that congenitally exposure to PCBs and thei
r contaminants has long-term adverse effects on the cognitive developm
ent of human being.