Radioisotopic kinetic studies of plasma triglyceride transport have been performed in rabbits treated with tetrachlorobiphenyls and compared with data obtained from untreated or olive oil-treated rabbits. Administration of tetrachlorobiphenyls provoked a rise of plasma triglyceride and an elevation of plasma triglyceride production rate but tended to lower the fractional turnover rate. The relationship of turnover rate to plasma concentration of triglyceride suggests that the increase of plasma triglyceride concentration observed in tetrachlorobiphenyl-treated rabbits can be accounted for by an increased production in some of cases, but in other cases glyceridemia is due primarily to a removal defect.