Behavioral problems were evaluated in Taiwanese children who were born between July 1978 and June 1985 to women who had consumed rice oil that was contaminated by heat-degraded polychlorinated biphenyls (PCBs). One hundred and eighteen such children, referred to as 'the early-born Yucheng children', and matched controls were followed with the Chinese version of Rutter's Child Behavior Scale A annually from 1985 to 1991. At any fixed age, the early-born Yucheng children had mean Rutter behavior scores 1.75 to 2.40 points higher (14-38% worse) than that of their controls. The effects were similar in the health, habit, and behavioral subscores and persistent as the children aged.