We investigate experimentally and theoretically nondegenerate four-wave mixing in rubidium vapor using a diamond configuration (5S(1/2), 5P(1/2), 5P(3/2), and 6S(1/2) levels). We model this process of three classical fields interacting with a four-level atomic system with the Schrodinger equation. The experimental results are in good agreement with theoretical predictions for the generated light as a function of detuning.