Gas chromatography has been applied for the analysis of organochlorine compounds of 49 samples of human milk. The average total DDT (2,2-bis(4-chlorophenyl)1,1,1-trichloroethane) content in human milk was found to be 0.058 mg/kg (1.57 mg/kg milk fat, with a range of 0.54-4.00 mg/kg). Thirty-four cases contained traces of dieldrin, but the content of dieldrin reached 0.008 mg/kg in only one milk sample. The average content of PCB (polychlorinated biphenyls) was 0.024 mg/kg of human milk, with a range of 0.011-0.054 mg/kg (0.65 mg/kg of milk fat with a range of 0.33-1.10 mg/kg). The ratio of DDT metabolites/DDT varied from 1.1 to 7.8 (mean 2.8). Studies were also made of the effect of the weight, weight loss, diet, smoking habits and parity of the nursing mother upon the content of organochlorine compounds in human milk. A significant positive correlation was observed between the DDT content of human milk fat and cigarette smoking. The average daily intake of total DDT for Finnish breastfed babies was calculated to be 0.0093 mg/kg, 1.9 times more than the daily intake of 0.005 mg/kg indicated by FAO/WHO as the acceptable value.