Objectives To monitor the residents prevalence of endemic arsenism in the disease affected areas in Inner Mongolia, so as to provide feasible suggestions for control of arsenism in the future. Methods Monitoring data were obtained from the Project of Endemic Disease Prevention Granted by Central Government in 2010 - 2012, and the conditions of arsenism patients from 38 endemic arsenic villages were analyzed among different year, age and gender. Results The detection rate of arsenism of the 38 surveillance villages was 7.38%(517/7 004) in 2010, 7.10%(482/6 784) in 2011 and 6.62% (431/6 514) in 2012. The arsenism patients of mild;moderate and severe cases from 2010 to 2012, accounted for 74.47% (385/517), 74.27% (358/482), 75.17% (324/431); 16.83% (87/517), 16.60% (80/482), 15.78% (68/431) and 8.7% (45/517), 9.13% (44/482), 9.05% (39/431), respectively. For skin lesions, the detection rates of keratosis, pigmentation and depigmentation from 2010 to 2012, were 8.08%(566/7 004), 7.90%(536/6 784), 7.77%(506/6 514);3.27%(229/7 004), 3.29%(223/6 784), 2.87%(187/6 514) and 6.68% (468/7 004), 6.63% (450/6 784), 5.82% (379/6 514), respectively, showed a declining trend. It also showed a declining trend with age, and the patients were mainly 40 years old people and older, and the highest detection rate was in the 60- 70 years old group[15.54%(143/920)、14.72%(135/917)、13.36%(136/1 018)]. For gender distribution, the detection rate of the three years was higher in male than female [male 8.24%(300/3 639), 7.99%(283/3 542), 7.71%(260/3 372);female 6.45%(217/3 365), 6.14%(199/3 242), 5.44%(171/3 142),χ2=8.24, 8.77, 13.54, all P〈0.01]. Conclusion There is no big change of arsenism conditions in 2010-2012, with a slight declining trend.