Twenty‐five blood and biopsy fat samples were collected from donors with and without a Down's Syndrome child, and analyzed for 29 selected polychlorinated biphenyl isomers. Differences in polychlorinated biphenyl isomer levels in blood and adipose tissue of donors with or without a Down's Syndrome child were not statistically significant. Most polychlorinated biphenyl Isomers observed in blood were also detected in adipose tissue, except for the 3,4,4'‐trichlorobiphenyl, which was sometimes observed in blood, but not in adipose tissue.