Adult primary brain tumors comprise a diverse group of neoplasms that vary in their behavior depending on such factors as cell of origin, site of occurrence, morphology, and pattern of spread. Although the incidence of primary brain tumors is increasing in frequency, the prognosis of patients with these neoplasms has improved considerably due to recent advances in microsurgery, radiation treatment, and chemotherapy. Central to the efficacy of these techniques, however, is the ability of the radiologist to diagnose and interpret the growth pattern of these tumors. This article describes various types of primary intracranial neoplasms found in the adult, with emphasis on imaging characteristics and their importance in neuro-oncologic evaluation and management.