Optical coherence tomography (OCT) is a technique for obtaining cross-sectional images of tissue with a resolution of approximately 10 μm and a depth of imaging of 1–2 mm (1). OCT is analogous to ultrasound (US) imaging, with reflected, near-infrared (1,300-nm) light measured instead of sound. This technique has been used to image several types of tissues, including blood vessels (2) and the eye (3). Because OCT detects light backscattered at index of refraction mismatches, it was anticipated that the gas-filled microbubbles would produce a strong OCT signal. In this study, the ability of microbubbles to enhance the OCT signal from a phantom, blood, and the eye was examined. A previous study using a 200-MHz phase modulation system found a change in the optical properties of a subcutaneous tumor when microbubbles were injected. This diffuse optical technique measured a mean photon path length increase at 754 nm (4). To our knowledge, this is the first study of the effects of microbubbles on OCT images.