The fluctuation theorem gives an analytical expression for the probability of observing second law violating dynamical fluctuations in nonequilibrium systems. At equilibrium, statistical mechanical fluctuations are known to be ensemble dependent. In this paper we generalize the transient and steady-state fluctuation theorems to various nonequilibrium dynamical ensembles. The transient and steady-state fluctuation theorem for an isokinetic ensemble of isokinetic trajectories is tested using nonequilibrium molecular dynamics simulations of shear flow.