Many Michigan farm children are viewed as having suffered a deterioration in health coincident with contamination of dairy cattle by PBBs. Among Wisconsin dairy farm children such a deterioration was a rare event. There is a suggestion that Michigan farm children who had multiple symptoms during the 1973-76 period are getting better. A discrete syndrome of ill health has not been identified among Michigan farm children. The symptoms complained of indicate a disruption of various physiological functions, including neurobehavioral, gastrointestinal and immunological. Children from quarantined farms do not have a higher prevalence of multiple symptoms than those from nonquarantined farms.