The mathematics of probability are used to construct a framework that describes some key features of primary and secondary creep. The underlying assumption is that dislocation slip and annihilation are probabilistic events. The resulting mathematical framework takes the form of renewal theory from probability theory. Renewal creep theory provides a mathematical frame-work for primary creep that accommodates previously developed empirical descriptions. Renewal creep theory also predicts the existence of secondary creep as an asymptotically constant strain-rate phenomenon. Creep modeling techniques are demonstrated for three titanium alloys.