Residue levels of the chlorinated hydrocarbons p,p'-DDT (2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane), p,p'-DDE (2,2-bis(p-chlorophenyl)-1,1-dichloroethane), hexachlorobenzene (HCB), alpha-, beta-, and gamma-hexachlorocyclohexane (HCH), aldrin, dieldrin, and polychlorinated biphenyls (PCBs) were determined in human milk of Kenyan mothers living in different areas of Kenya. The main organochlorine contaminants found in all the milk samples analyzed were p,p'-DDT and p,p'-DDE. Great regional differences were found, and mean levels of sum DDT and DDT/DDE ratio ranged from 1.1 to 18.7 mg/kg milk fat and from 0.7 to 5.7, respectively. In general, relatively low residue levels of HCB, alpha-HCH, beta-HCH, aldrin, and dieldrin were detected in 59, 37, 27, 37, and 19%, respectively, of all the milk samples analyzed. Quantifiable residue levels of PCBs and alpha-HCH were not found. The results were examined in relation to differences in living conditions with regard to agricultural activities, dietary habits, and reported use of pesticides in the various sampling areas.