  We study here the evolution of a massless scalar field in a spacetime,
developing from a regular initial spacelike surface. The Einstein equations and
regularity and boundary conditions governing the same are specified. Both
homogeneous and inhomogeneous collapse models are considered and we analyze
when the occurrence of singularity will be simultaneous or otherwise. In the
inhomogeneous collapse case, we characterize a wide family of black hole
solutions arising in scalar field collapse. We also discuss the possibility of
existence of classes of non-singular models where collapse could almost freeze
if suitable conditions are satisfied.
