Farnesyl protein transferase (FPT) is a promising target for the development of cancer chemotherapeutics because it is responsible for the farnesylation of oncogenic p21 Ras proteins which are found in nearly 30% of all human cancers and necessary for cellular development and growth. The recent discovery and progression to phase II clinical trials of trihalobenzocycloheptapyridine Sch-66336 as a potent inhibitor of FPT with oral, in vivo efficacy in mice have spawned extensive structure-activity relationship studies (SAR) of this class of compounds. Of the many trihalobenzocycloheptapyridine analogues prepared, we have identified several which inhibit FPT and cellular proliferation at single-digit nanomolar concentrations and which have good pharmacokinetic properties in mice.