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Ductal carcinoma in situ (DCIS) is a noninvasive cancer that accounts for 25% of all breast cancers diagnosed in the United States. DCIS is a heterogeneous disease process with varied clinical manifestations and a broad spectrum of imaging findings. With advances in technology, the ability to detect early-stage cancers has improved, and understanding the role of ultrasonography (US) in the multimodality era of detection and diagnosis is paramount. When calcifications are identified at mammography, US can be performed to evaluate for an invasive component and to allow possible US-guided biopsy. Use of high-frequency transducers, spectral compounding, and speckle reduction algorithms can aid in the detection of calcifications. Calcified DCIS most commonly manifests as echogenic foci located within a mass or duct, associated with internal microlobulations, or distributed in a branch pattern. Noncalcified DCIS, which is more often identified in symptomatic patients, may manifest as a hypoechoic mass with microlobulated margins and no posterior acoustic features, or it may have a "pseudomicrocystic" appearance. Harmonic imaging and coronal reconstruction may improve detection of noncalcified DCIS. The appearance of DCIS at "second-look" US can be subtle and may warrant a lower threshold for detection, given a higher pretest probability of malignancy. US features are nonspecific, and careful correlation with respect to lesion location, size, shape, and depth is needed. The presence of internal vascularity can help increase the positive predictive value of US in this setting. US is a useful adjunct to mammography and magnetic resonance imaging, and recognizing the US appearance of DCIS will aid in the detection and diagnosis of this disease entity.