We present results of mixed quantum-classical molecular dynamics simulations of the intramolecular proton transfer in acetylacetone. Simulations are performed starting from the reactant and transition state configurations with initial velocities at each configuration chosen from an ensemble at 300 M. The proton motion is treated quantum mechanically and the remaining degrees of freedom are treated classically. Two mixed quantum-classical molecular dynamics methods are implemented. In the first, a quantum-classical time-dependent self-consistent field method (QC/TDSCF), the time-dependent Schrodinger equation for the proton is solved using the split operator approach and a plane-wave basis. In the second, a mixed quantum-classical adiabatic method (QC/A), the instantaneous ground state wave function is calculated by solving the time-independent Schrodinger equation for the configurations of the classical particles by propagating in imaginary time using the split operator approach and the same plane-wave basis. A comparison of the two approaches with classical trajectories is presented. The QC/TDSCF and QC/A results are very similar for trajectories started from the reactant configuration, The two methods, however, yield somewhat different results when the trajectories are started from the transition state configuration. The proton wave function of the QC/A method adjusts instantaneously to the position of the classical particles, whereas the motion of the QC/TDSCF wavepacket more faithfully represents the true proton dynamics. (C) 1997 John Wiley & Sons, Inc.