Samples of 24-h urine were collected from 278 subjects (159 males and 119 females) in 1985, and 321 subjects (161 males and 160 females) in 1993 in the same factory with no occupational exposure to lead (Pb) in Japan. The age range of the subjects was 20-59 years. The urinary Pb concentrations were analyzed by flameless atomic absorption spectrophotometry after wet digestion followed by solvent extraction. The Pb levels in 24-h urine were distributed log-normally with geometric means (geometric S.D.) of 4.74 (1.46) and 2.67 (1.98) micrograms/day for males; and 3.22 (1.42) and 2.14 (2.05) micrograms/day for females in 1985 and 1993, respectively. No age-related changes in Pb levels in 24-h urine in either sex from 20 to 59 years were apparent. Pb levels in 24-h urine were significantly higher in males than in females (P < 0.01). Analysis of male smokers together with age-matched non-smokers failed to show an elevation of Pb levels in 24-h urine as related to smoking habits. Comparison of the Pb levels in 24-h urine in 1985 and 1993 disclosed that the Pb levels in 24-h urine were significantly lower in 1993 than in 1985 in both sexes (P < 0.01).