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Phase imaging is an important source of contrast when studying the brain, body, and musculoskeletal systems. Gradient echo (GRE) sequences are typically used with echo times (TEs) of 10–40 ms to allow time for appreciable phase evolution. Ultrashort echo time (UTE) imaging sequences employ much shorter TEs to detect short-T₂ signals, limiting the time available to develop significant phase differences. Still, surprisingly, high phase contrast (PC) can be achieved with UTE sequences using TEs far shorter than those previously used for susceptibility-weighted imaging (SWI). This chapter focuses on UTE phase imaging of short-T₂ tissues. The theory, experimental verification, and specimen studies are briefly discussed. Applications in the lung, brain, and vasculature are highlighted.