  We investigate the Cauchy problem for the Einstein - scalar field equations
in asymptotically flat spherically symmetric spacetimes, in the standard 1+3
formulation. We prove the local existence and uniqueness of solutions for
initial data given on a space-like hypersurface in the Sobolev $H_1\cap H_{1,4}
$ space. Solutions exist globally if a central (integral) singularity does not
form and/or outside an outgoing null hypersurface. An explicit example
demonstrates that there exists a local evolution with a naked initial curvature
singularity at the symmetry centre.
