Ultrasonic imaging has been used in the field of dermatology for nearly 30 years. In this review, we seek to explain the basic principles of ultrasound as they relate to the skin. Based on differences in keratin, collagen, and water content, ultrasonic waves are reflected back to a transducer and translated into a gray-scale image for interpretation. The technicalities of the process and its variations (power, continuous wave Doppler ultrasound, ultrasound elastography) are briefly reviewed, and we further highlight many of the applications for ultrasound in the treatment and diagnosis of dermatologic conditions, including melanoma and nonmelanoma skin cancer, benign tumors, inflammatory diseases, and lipoablation. Each of these entities is uniquely characterized using ultrasonic techniques. Based on published sources, we contend that although ultrasound is still being fine-tuned for application in dermatology and largely remains in experimental phases, it has potential for use in many arenas of our specialty.