Regional Occupational Health Centre (Eastern) (Indian Council of Medical Research), Block DP, Sector V, Salt Lake, Kolkata-700 091, India E-mail : ashit_mukherjee@yahoo.com Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata-700 032, India Manuscript received 27 June 2017, revised 07 September 2017, accepted 17 November 2017 Arsenic contamination in ground water has been received much attention in recent times because of its carcinogenicity. Chronic exposure to arsenic through drinking water causes several multi-organ diseases including cancer. This study reports urinary porphyrins profile as a mark of disturbances in heme biosynthetic pathway due to chronic exposure to arsenic contaminated drinking water in endemic area of North 24- Parganas district of West Bengal. Arsenic in drinking water and urine were measured respectively by flow injection analysis system – Atomic Absorption Spectrometry (FIAS-AAS) and Transversely heated graphite atomizer (THGA-AAS) techniques. Urinary porphyrins were estimated simultaneously by reverse phase HPLC. Arsenic level in water was >50 µg/L in 57.7% tube wells, of which 13.3% were, >500 µg/L. Urinary arsenic (µg/g creatinine) was found to increase with increasing exposure. Study showed altered urinary porphyrins with changes in water arsenic (W-As) content as well as with duration of exposure. Higher porphyrin levels were observed in group, exposed to water arsenic, >250 µg/L, having exposure, ≥ 15 years, irrespective of gender. Significant differences between urinary porphyrins and duration of exposure of the subjects was noticed in the cases, uro III (p < 0.001), penta I (p < 0.05), copro III (p < 0.001) and the ratio of copro III/ uro III (p < 0.05). An increasing trend of urinary porphyrins noticed with exposure to arsenic, though the difference between urinary porphyrins and exposure to water arsenic was insignificant. The study suggests that urinary porphyrins may serve as biomarker of chronic exposure to arsenic among population in the endemic area.