simplest of systems is poorly understood, in so far as cosmic censorship is concerned. It is of course true that spherical collapse, if allowed to proceed to completion, results in a Schwarzschild black hole. However, a spherical collapsing system can also admit timelike or null singularities which can be naked. From the point of view of an observer falling with the star this can happen if a singularity forms inside the star (say at its center) before the boundary of the star enters its Schwarzschild radius. Such a singularity can be naked.

Since the exact solution of Einstein equations for spherical collapse with a general form of matter is not known, collapse of matter with various equations of state has been studied. In the following pages, we review some of these results.

Spherical Dust Collapse
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Historically, the earliest model of gravitational collapse is due to Oppenheimer and Snyder. They showed that the collapse of a homogeneous dust sphere results in the formation of a black hole (by dust is meant an idealized perfect fluid for which the pressure is zero). It was thought that the formation of the black hole will not be affected even if the specialized assumptions 