Research on intelligent tutoring seeks to develop systems for automating education and to explore epistemological issues concerning the nature of the knowledge presented by tutors and how that knowledge can be learned. The ACT theory of skill acquisition and its successor (PUPS--PenUltimate Production System) provides production-system models of the acquisition of skills such as LISP programming, geometry theorem-proving, and solving of algebraic equations. The three major sections of the document discuss; (l) the cognitive theory that serves as the basis for the tutoring endeavors, (2) the model-tracing methodology and how it derives from the cognitive theory, and (3) issues that arise in implementing the methodology. Knowledge begins in declarative form and is used by analogical processes to solve specific problems. Domain-specific productions are compiled from the traces of these problem solutions. The model-tracing methodology has been developed as a means of displaying this cognitive theory in intelligent tutoring. Implementation of the methodology involves developing a student model, a pedagogical module, and an interface. Work on tutoring and on skill acquisition have proven to be symbiotic -- each has furthered the other's development. (Author/MNS)