OBJECTIVES: We investigated whether UK military personnel exposed to sarin during the 'Service Volunteer Programme' at Porton Down had increased rates of mortality or cancer incidence over a 52-year follow-up. METHODS: A historical cohort study assembled from UK military records, comprising male veterans exposed to sarin during the 'Service Volunteer Programme' at Porton Down, UK (n=2975) and a comparison group of similar veterans who did not attend (n=2919). Mortality and cancer incidence data were obtained from national registries up to December 2019. Analysis was conducted using Cox regression adjusted for age, year of birth and service characteristics. RESULTS: Over a median follow-up of 52.2 years (range 2 days to 74.6 years), 1598 (53.7%) sarin-exposed veterans and 1583 (54.3%) non-exposed veterans died. Adjusted HRs for all-cause mortality were raised for any sarin exposure (HR=1.08, 95% CI 1.01 to 1.16), two or more exposures (HR=1.25, 95% CI 1.04 to 1.49) and higher doses (air >15 mg.min/m3) (HR=1.15, 95% CI 1.02 to 1.30). For cause-specific mortality, sarin exposure was associated with deaths from 'other' circulatory diseases (excludes ischaemic and cerebrovascular diseases) (HR=1.41, 95% CI 1.06 to 1.87) and alcohol-attributable deaths (HR=2.66, 95% CI 1.40 to 5.07). There was no association between sarin exposure and overall cancer incidence (HR=1.01, 95% CI 0.93 to 1.10), but cancer incidence was higher for alcohol-related neoplasms (HR=1.24, 95% CI 1.01 to 1.51). CONCLUSIONS: Sarin exposure was associated with increased rates of mortality over a 50-year follow-up. The strongest associations were observed for deaths attributable to alcohol and 'other' circulatory diseases.