That smallpox was a leading cause of death in China in the eighteenth and nineteenth centuries is widely accepted, but this has rarely been documented quantitatively. Instead the prevalence of smallpox is inferred from scattered reports of epidemics, impressionistic reports of the numbers pockmarked by the disease, and from reports of efforts to staunch the disease through variolation and vaccination. Nor has the extent of vaccination in the population of late nineteenth century China ever been assessed quantitatively. This paper, after a brief review of the reported history of smallpox and vaccination in Taiwan, analyzes a unique source of evidence from the Taiwan household registers created in 1905 that provides quantitative measures of the smallpox and vaccination status of the island's population in the late nineteenth century.