Mortality and morbidity of vascular diseases, including stroke, are known to be associated with chronic exposure to inorganic arsenic through drinking water. A tap-water supply system was implemented in the early 1960s in the blackfoot disease (BFD) endemic areas of Taiwan. The objective of this study was to examine whether mortality attributed to stroke decreased among residents living in the BFD-endemic areas after the curtailment of arsenic exposure. Further it was of interest to determine whether arsenic exposure was related to a specific type of stroke. Standardized mortality ratios (SMRs) for stroke were calculated for the BFD endemic area for the years 1971-2000. The study results show that mortality due to primary intracerebral hemorrhage (PIH) declined gradually after the improvement of drinking-water supply system by elimination of arsenic exposure through removal of artesian well water. Based on the reversibility and specificity criteria, the association between arsenic exposure and mortality due to PIH is likely to be causal.