Arsenic contamination of groundwater and associated medical problems have long been reported in the Mushidabad district, one of nine arsenic-affected districts in West Bengal, India. In order to estimate people's total exposure to arsenic, we visited 12 arsenic-affected families in that area during 4-7 December 2000 and collected seven tubewell waters used for drinking, cooking and other household purposes and 51 urine samples from those families. The arsenic concentrations in drinking water ranged from 2.7 to 170 ppb. Those families designated A-E, G-I and J took in arsenic concentrations of 72.6 ppb, 154 ppb and 170 ppb respectively. The concentrations of arsenite, arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in urine (corrected for creatinine level in the urine), obtained from 51 persons, ranged from 0 to 796.9 ppb (mg creatinine/ml urine)-1, from 0 to 1635.2 ppb (mg creatinine/ml urine)-1, from 2.1 to 411.0 ppb (mg creatinine/ml urine)-1 and from 8.3 to 2017.5 ppb (mg creatinine/ml urine)-1 respectively. The average concentration of total arsenic was 59.2 ppb (mg creatinine/ml urine)-1. On comparison of the ratios of (MMA + DMA) to total arsenic, the average proportion of (MMA + DMA) was 83.2%, but the proportions were 27.3% and 16.5% for two of the children (2 years old and 13 years old respectively). This result suggested that they might be damaged due to the methylating capacity. When estimating arsenic species in urine obtained from families A-E, G-I and J, these family members normally metabolized the inorganic arsenic to MMA and DMA and eliminated these as such in comparison with an intake of inorganic arsenic from the tubewell water. The arsenic species in urine from people having the same food and life habits showed the same profile in both men and women. There was a good correlation (p < 0.05) between the ages of 19 persons in families A-E and the values of (MMA + DMA) or total arsenic in urine. Copyright © 2002 John Wiley & Sons, Ltd.