Comprehensive Monte Carlo simulations of the short-time dynamic behaviour are reported for the three-dimensional Ising model at criticality. Besides the exponent θ of the critical initial increase and the dynamic exponent z, the static critical exponents ν and β as well as the critical temperature are determined from the power-law scaling behaviour of observables at the beginning of the time evolution. States of very high temperature as well as of zero temperature are used as initial states for the simulations. PACS: 64.60.Cn, 75.10.Hk, 64.60.Ht, 75.40.Mg * Work supported in part by the Deutsche Forschungsgemeinschaft; DFG Schu 95/9-1 and SFB 418 1 For a recent review see Ref. [2].