Hair and mercury concentrations of 134 fish-eating subjects in the Lake Murray area and 13 non-fish-eating subjects in the upper-Strickland area, Papua New Guinea, were studied. Hair mercury levels among the subjects in the Lake Murray area (mean = 21.9 micrograms/g, range = 3.7-71.9 micrograms/g) and urinary mercury levels (mean = 7.6 micrograms/g creatinine, range = 1.4-25.6 micrograms/g creatinine) were markedly higher than levels found in subjects from the upper-Strickland area (mean hair mercury = 0.75 micrograms/g, mean urinary mercury = 0.48 micrograms/g creatinine). Mercury intake of the fish eaters, estimated from mercury concentrations found in fish and from the observed amounts of fish consumed, was approximately 73 micrograms/d. Hair and urinary mercury concentrations were correlated significantly (r = .59), indicating that urinary mercury excretion was elevated because fish consumption was very high.