The process of pitch angle scattering by a current sheet is studied using the modified Harris field model. The relationship between the incoming asymptotic pitch angle &agr;in and the outgoing asymptotic pitch angle &agr;out is studied from first principles by numerically integrating the equation of motion. We give evidence that charged particles undergo chaotic scattering by the current sheet. For fixed &agr;in, it is shown that &agr;out exhibits sensitive dependence on the energy parameter Hˆ in certain energy ranges. For fixed Hˆ in the same energy ranges, &agr;out sensitively depends on &agr;in. For other energy values, &agr;out does not show sensitive dependence on &agr;in for most phase angles. The latter energy values occur at the resonance values given by the previously identified relationship Hˆ1/4~N+0.6. Thus &agr;out exhibits no significant sensitivity near these resonance energies. This conclusion applies to a range of &agr;in centered at &agr;in=0 (i.e., field aligned in the asymptotic region). A distribution of &agr;in is mapped from the asymptotic region to the midplane, and it is found that the resulting particle distribution should have beam structures with well-collimated pitch angles near each resonance energy value. Implications for the particle distribution functions in the Earth's magnetotail are discussed. ¿ American Geophysical Union 1992