The Annual Reports of the Registrar-General for England contain each year, tables giving information as to the mortality in the Navy and Army for a long series of years. My object in undertaking this paper was to compare the actual death-rates, as shown in these tables, with the rates prevailing among assured lives, with a view to ascertaining the extra mortality to which persons serving in the Navy and Army are subject. I subsequently found it desirable to extend the scope of the paper so as to include an examination of the recent mortality of the Navy, as shown by the Statistical Reports of the Health of the Navy, and of the Army, as shown by the Reports of the Army Medical Department.