We derive, for spacetimes admitting a Spin(7) structure, the general local
bosonic solution of the Killing spinor equation of eleven dimensional
supergravity. The metric, four form and Killing spinors are determined
explicitly, up to an arbitrary eight-manifold of Spin(7) holonomy. It is
sufficient to impose the Bianchi identity and one particular component of the
four form field equation to ensure that the solution of the Killing spinor
equation also satisfies all the field equations, and we give these conditions
explicitly.Comment: 9 pages, latex. v2: change of title (formerly known as "Spin(7)
structures in eleven dimensions"); short section on integrability conditions
added, various minor changes. To appear in Phys.Rev.Let