This study was carried out to investigate the levels of copper, zinc, manganese, nickel, cadmium and mercury content in breast milk among urban, rural and industrial lactating women in Korea. A total of 59 samples, which were collected from 17 in urban, 20 in rural and 22 in industrial area, and from 21-38 years-old healthy lactating women, were analyzed by Rigaku Mercury Analyzer for mercury, and by atomic absorption apectrophotometry for the other metals. The results are summarized as follows : The mean trace metal contents in breast milk were determined to be 0.34$pm$0.14 ppm for copper, 2.01$pm$1.43 ppm for zinc, 8.49$pm$5.11 ppb for manganese, 7.75$pm$5.73 ppb for nickel, 1.65$pm$2.42 ppm for cadmium, 34.45$pm$26.71 ppb for lead and 0.90$pm$0.68 ppb for mercury. For the trace metal content in breast milk by area, the highest of copper, zinc, cadmium and mercury content were in urban, the highest of manganese content was in industrial, and the highest of nickel and lesd content were in rural. For copper, zinc, manganese and lead content in breast milk by lactation period, the highest levels were found in under 4 weeks after lactating, and subsequently the levels declined as lactation progressed, but the levels of zinc and manganese content increased from over 25 weeks after lactating. For cadmium and mercury content in breast milk by lactation period, the lowest levels were found in under 4 weeks after lactating, the highest levels were found in 5-12 weeks after lactating, and subsequently the levels declined as lactation progressed.For nickel content in breast milk by lactation period, the highest level was in 13-24 weeks after lactating, the lowest level was in 5-12 weeks after lactating.