In this note, the interaction factors for the analysis of axially loaded pile groups are calculated using a procedure that makes use of the stiffness matrices for the study of wave propagation problems involving layered media. As a result, static as well as dynamic analysis of piles can be achieved within the same framework, and the soil layering effect is reliably accounted for. The theoretical predictions from the proposed method are compared with experimental measurements from published static and dynamic load tests on pile groups.