We consider the spherically symmetric, asymptotically flat Einstein-Vlasov system. We find explicit conditions on the initial data, with ADM mass M, such that the resulting spacetime has the following properties: there is a family of radially outgoing null geodesics where the area radius r along each geodesic is bounded by 2M, the timelike lines r = c ∈ [0, 2M ] are incomplete, and for r > 2M the metric converges asymptotically to the Schwarzschild metric with mass M . The initial data that we construct guarantee the formation of a black hole in the evolution. We also give examples of such initial data with the additional property that the solutions exist for all r ≥ 0 and all Schwarzschild time, i.e., we obtain global existence in Schwarzschild coordinates in situations where the initial data are not small. Some 1 of our results are also established for the Einstein equations coupled to a general matter model characterized by conditions on the matter quantities.