In the observational study of social systems, the major conceptual innovation in this century has been General Systems Theory. Yet the General Systems Theory conceptions of interacting social systems were doomed to remain at the prescientific level of metaphor until a set of statistical techniques were developed and applied. These techniques have come to be known as sequential analysis. Sequential analysis has as its first objective the detection of recurring sequential patterns in a stream of coding categories describing social interaction. These techniques can be employed to study the repertoires of individuals.