This chapter discusses anterior skull base tumors, where anterior cranial fossa (ACF) is bound anteriorly by the frontal bone, inferiorly by the orbital roofs, posterior laterally by the greater wing of the sphenoid, and posterior medially by the lesser wing of the sphenoid and anterior clinoid process. The crista galli is an osseous ridge arising from the midline of the ethmoid bone, where planum sphenoidale and the lesser wing of the sphenoid constitute the posterior floor of the anterior cranial fossa behind the cribriform plate. The lesions of the ACF can be broadly divided into congenital, inflammatory, traumatic and neoplastic, where the tumor cells are usually positive for neuron specific enolase, chromographine, synaptosin and Leu-7. Adenocarcinomas occur in approximately 35 percent and primarily arise in the ethmoid sinuses or in the upper nasal cavity.