The aim of this study was to evaluate use of the microblogging social network Twitter by academic radiology departments (ARDs) in the United States. Twitter was searched to identify all accounts corresponding with United States ARDs. All original tweets from identified accounts over a recent 3-month period (August to October 2014) were archived. Measures of account activity, as well as tweet and link content, were summarized. Fifteen ARDs (8.2%) had Twitter accounts. Ten (5.5%) had "active" accounts, with ≥1 tweet over the 3-month period. Active accounts averaged 711 ± 925 followers (maximum, 2,885) and 61 ± 93 tweets (maximum, 260) during the period. Among 612 tweets from active accounts, content most commonly related to radiology-related education (138), dissemination of departmental research (102), general departmental or hospital promotional material (62), departmental awards or accomplishments (60), upcoming departmental lectures (59), other hospital-related news (55), medical advice or information for patients (38), local community events or news (29), social media and medicine (27), and new departmental or hospital hires or expansion (19). Eighty percent of tweets (490 of 612) included 315 unique external links. Most frequent categories of link sources were picture-, video-, and music-sharing websites (89); the ARD's website or blog (83); peer-reviewed journal articles (40); the hospital's or university's website (34), the lay press (28), and Facebook (14). Twitter provides ARDs the opportunity to engage their own staff members, the radiology community, the department's hospital, and patients, through a broad array of content. ARDs frequently used Twitter for promotional and educational purposes. Because only a small fraction of ARDs actively use Twitter, more departments are encouraged to take advantage of this emerging communication tool.