This document describes the process of porting Pan I from Franz Lisp to Allegro COMMON LISP. It focuses on issues relevant to Pan, but is intended to supply guidelines on porting any large Lisp system. The steps taken to translate the code were designed to keep the Franz implementation functional while the Allegro implementation was being developed. Three techniques were used. Franz code was rewritten to be compatible with both Lisps. Franz macros were introduced to duplicate Allegro functionality. Lastly, conditional compilation was used to allow the coexistence of both Franz and Allegro versions of code in situations that proved too cumbersome for the first two techniques.