The developer of the two-cone model of second language teaching and learning outlines the original model and its concepts, and presents some further ideas concerning it. The model represents the native and second languages as two cones with pronunciation at the apex, morphology and syntax (grammar) at the center, and vocabulary around grammar and at the cone's base. The interaction of the two languages during the second language learning process is represented as the union and integration of the cones at various stages and according to the quality of instruction. Further observations suggest that the model (1) is centrifugal, involving movement from the center to the communicative outer edge, in contrast to native language acquisition; (2) incorporates certain basic pedagogical principles of selection, ordering of components, gradation, correction, practice toward mastery, and progressive integration; (3) accounts for both interference and overgeneralization; and (4) relies on the principle of communication following mastery. In addition, the two cone model is compared with two other models, Selinker's interlanguage hypothesis and Krashen's Monitor Model, and its relationships to learning theory, linguistics, and second language methodology are briefly discussed. (MSE)