Adenomyosis is a common but under-diagnosed gynecologic condition due to hypertrophied myometrial smooth muscle containing ectopic endometrial glands that is associated with pelvic pain, menorrhagia, and an enlarged uterus. This is an overview of the sonographic and magnetic resonance imaging features that have been developed in the diagnosis of adenomyosis emphasizing sonography as the initial study performed in the symptomatic patient. These features include myometrial heterogeneity, asymmetric thickening of myometrium, cysts, linear striations, and an ill-defined endometrium. Both magnetic resonance imaging and sonography can now diagnose adenomyosis with a high degree of accuracy so that treatment may be instituted specific to the disease process.