Abstract: This invention is an adjustable multi-purpose knife structure operable to fillet fish and cut selected thickness of meat, cheese, or the like. The adjustable multi-purpose knife structure includes first and second handle and blade assemblies interconnected by a connector and guide assembly and movable relative to each other by an actuator assembly. Each handle and blade assembly includes a blade member secured to a handle member. The connector and guide assembly includes spaced guide pin members operably connected to the adjacent first and second handle and blade assemblies to control the respective lateral movement thereof. The actuator assembly includes an actuator wheel assembly connected to and mounted between the first and second handle and blade assemblies and an actuator lock assembly mounted in one of the handle members. The actuator wheel assembly includes an actuator member that is rotatable to selectively move the first and second handle and blade assemblies toward or away from each other.