To further investigate the prevalence of tumors of the bladder in areas where blackfoot disease is endemic or non-endemic, 327 diagnosed tumor cases were followed up. Resulting data were analysed and compared by age of onset, sex, tumor differentiation and stage, invasive tumor recurrence post-operatively and prognosis for patients from areas endemic (n=119) and non-endemic (n:108) for blackfoot disease. This study demonstrated that age at tumor onset, sex, tumor differentiation and tumor stage showed no statistically significant differences between the two groups (P>0.05). However, 36% of the patients in the blackfoot endemic areas developed invasive recurrent tumors; 17.2% of those in the non-endemic areas also developed such tumors. This is a statistically significant difference (P<0.05). The high-risk villages on Taiwan were the districts of Putai, Ichu, Hsuehchia and Peimen districts. A high content of arsenic in the Artesian well water used there may be an important cancer determinant in these areas. It is suggested that periodic, but regular, follow-up be done for residents of the blackfoot disease area, with screening of urinary cytology as well. Further, the Artesian well water should be replaced with a piped water supply as the most effective disease prevention method.