Numerous plastic devices and materials used for medical, dental, and food collection, processing, and packaging are made of polyvinyl chloride) and plasticized mainly with di-2-ethylhexyl phthalate (DEHP) to impart the desired physical and chemical characteristics. Some finished products may contain more than 40% plasticizer, which may be leached from the material by blood (1) or milk (2) or various other solutions. DEHP has generally not been considered to be a health hazard because of its low acute oral toxicity (3-10) and because the amount of DEHP leached from plastics is quite small. However, there is evidence that DEHP is not readily hydrolyzed but accumulates in body tissues. When two patients were infused with blood stored in plastic blood bags plasticized with DEHP, Jaeger and Rubin (11) found DEHP in the spleen, liver, lung, and abdominal fat in concentrations ranging from 2.5 to 27 mg-% (dry weight). The teratogenic effects of several phthalate esters when injected into the yolk sac or allantoic cavity or applied to the chorioallantoic membrane of developing chick embryos have been reported by Haberman and others (12-14). More recently, tDepartment of Dairy Science, Michigan State University, East Lansing, Michigan 48823. *To whom reprint requests should be sent. *Supported by the Michigan Agricultural Experiment Station (journal article 6113). Singh et al. (15) have reported the teratogenicity of phthalate esters in rats without regard to the effect these compounds might have on parturition. The present study was undertaken to determine the effects of dibutyl phthalate, dimethyl phthalate, and di-2-ethylhexyl phthalate on embryonic development and parturition.