UBV and narrow-band light curves for the eclipsing binary R CMa are obtained from a total of 977 narrow- and broad-band U, B, V, and H-beta photoelectric observations of the system. The light curves are found not to exhibit any conspicuously peculiar features, but the presence of asymmetries in the secondary minima of the V and narrow-band H-beta light curves is noted. Color indices in excellent agreement with those previously published are determined, out-of-eclipse variations are examined, and an eclipse analysis is performed. The absolute magnitudes and photoelectric indices of the hot and cool components are obtained, and a system mass ratio of 0.15 is estimated. The results indicate that: (1) R CMa is composed of a normal F0 main-sequence star plus an unusual K3 subgiant and is essentially free of interstellar absorption; (2) the more massive and larger F0 star is nearly spherical while the smaller and cooler component is highly distorted and just within its Roche lobe for the estimated mass ratio; (3) the observed luminosity of the secondary is substantially below that expected for an evolved star undergoing mass loss; (4) the rapid phase of mass transfer has apparently already taken place; and (5) circumstellar gas is probably present in the system.