Organochlorine residues (OCR)2 are poorly soluble in water and are transported in the organism bound by the blood components. The distribution among blood fractions (cells/plasma, lipoproteins/rest of plasma proteins) were variable depending on the residue (HCB, p p'-DDE, HCH, Aroclor 1260, PCP) and on the species (rat, man). Differences were not found between in vivo (after oral single dosing) and in vitro (blood incubation) experiments. Results indicated a high affinity of organochlorine residues for lipoproteins; however, binding to blood carriers was very weak as demonstrated by the rapid release of residues by elution through a reverse phase column. The effects of residue binding to blood components on the distribution kinetics to tissues are discussed.