Three dimensional hybrid simulations with particle ions and fluid electrons are used to calculate the kinetic evolution of the Kelvin-Helmholtz (K-H) instability for the simplest configuration, that of plasma with uniform density imbedded in a uniform magnetic field. The relative angle of the magnetic field and the velocity vector is varied, and for some simulations the magnetic field undergoes a rotation at the velocity shear layer. The results from the three-dimensional simulations are generally consistent with two-dimensional simulations, providing that the appropriate geometry is simulated in the two-dimensional cases. The simulations suggest that even modest rotation of the magnetic field across the boundary layer strongly reduces the nonlinear development of the instability so that its possible occurrence at the dayside magnetopause is greatly inhibited. ¿ American Geophysical Union 1995.