We investigated the interaction between larvae of two anuran amphibian species (Rana temporariaand Bufo bufo) to test models of two-species competition. The study had a response surface experimental design with four replicates, each consisting of 24 density combinations. Larval performance—and, by assumption, change in population size—was defined by a linear combination of survival, growth, and development. We fit six competition models from the literature and discovered that density dependence was strongly non-linear, with the highest support for the Hassel–Comins model. Rana temporariawas competitively superior to B. bufo; the impacts of both species on growth and development were about five- to tenfold greater than those on survival. Isocline analysis predicted a stable configuration, which agrees with the observation that these two species are syntopic in nature. The results of this study confirm competition theory by identifying a model structure that agrees with data and making predictions that are broadly supportive of the observations.