The Neutrino Factory and Muon Collider Collaboration (MC) comprises about 140 U.S. and non-U.S. accelerator and particle physicists. The MC is carrying out an R and D program aimed at validating the critical design concepts required for the construction of such machines. We are committed to encouraging international cooperation and coordination of the R and D effort. Main activities of the MC include a Targetry program, a MUCOOL program, a component development program, and a theory and simulation effort. Moreover, the MC has participated in several feasibility studies for a complete Neutrino Factory facility, with the aim of identifying any additional R and D activities needed to prepare a Zeroth-order Design Report (ZDR) in about two years and a Conceptual Design report (CDR) about two years thereafter. In this paper, the R and D goals in each area will be indicated, and the present status and future plans of the R and D program will be described.