A method to calculate volumetric distributions of contributon flux and contributon current is developed utilizing only the forward Monte Carlo approach. Various aspects of tracking contributons are discussed. Basically, the new method consists of sampling secondary particles at collision points occurring within a prespecified volume. A simple connection between integrals over that volume and surface integrals of contributon current is derived, thus providing a means of calculating integral detector responses via a volume integration of the contributon current. This leads to a considerable improvement of the effectiveness with which deep penetration radiation transport problems can be solved relative to analog Monte Carlo. A theoretical and numerical comparison of the performance of this new method with the performance of analog Monte Carlo techniques is carried out. Numerical results are discussed, and a theoretical model to predict the relative advantage of the new method was found to give satisfactory answers. If no biasing techniques are employed in either method, our sample problems show that the contributon method can save up to 90% of computing time over the conventional Monte Carlo method in deep penetration problems when computing an integral response with the same target accuracy.