Persistent organic pollutants (POPs) continue to threaten the environment and human health. We have investigated levels of polychlorinated biphenyls (PCBs) and organochlorinated pesticides (OCPs) in breast milk samples. A questionnaire was also obtained from the study participants. A total of 48 healthy lactating mothers (mean age: 29.5 +/- 0.8 years) living in Istanbul volunteered to participate in this study. High-resolution analyses of several OCPs and PCB congeners were done by gas chromatography. The levels of seven major PCB congeners (28, 52, 101, 118, 138, 153, and 180) and eight OCPs (alpha-benzenehexachloride, beta-benzenehexachloride, delta-benzenehexachloride, hexachlorobenzene (HCB), and 2,4 '-dichlorodiphenyldichloroethylene (2,4DDE), 4,4 '-dichlorodiphenyldichloroethylene (4,4DDE), 2,4 '-dichlorodiphenyltrichloroethane (2,4DDT), and 4,4 '-dichlorodiphenyltrichloroethane (4,4DDT)) were determined. The analysis showed that the highest levels of PCBs were observed in PCB 52 (22.99 +/- 8.78 ng/g lipid), PCB 101 (12.22 +/- 7.8 ng/g lipid), PCB 28 (11.44 +/- 5.16 ng/g lipid), and PCB 153 (1.70 +/- 0.74 ng/g lipid). The highest OCPs detected were 4,4DDT (3.33 +/- 2.05 ng/g lipid) and 4,4DDE (0.86 +/- 0.39 ng/g lipid), and the lowest was observed in HCB (0.016 +/- 0.01 ng/g lipid). Our findings show that traces of PCBs and OCPs are still present in breast milk of lactating women living in Istanbul, and these pollutants decline in multipara women compared to primipara mothers. We also suggest that breast milk is a useful and representative biological tool for human biomonitoring of POPs.