A typology of role-playing and simulation exercises based on interpersonal interactions, used in second language instruction, is presented. Ten dimensions of such simulations were identified, which can then be used as criteria for classifying the exercises. The dimensions include: the starting point of the simulation; complexity of the conversation to be simulated; quantity of available data; degree of constraint in data; degree of creativity/imitation expected of the learner; degree of freedom given to the learner in defining the case; degree of planning afforded to the learner; presence of potential elements of dramatic tension; foreseeability of the language outcome; and relation to reality. The resulting typology produces three simulation types and eight sub-types. The research offers parameters to be taken into account when creating simulations, selecting them for specific pedagogical purposes, and researching them as a classroom learning tool. Contains 421 references. (MSE)