The ability of ultra-high-resolution optical coherence tomography (UHR OCT) to discriminate between healthy and pathological human brain tissue is examined by imaging ex vivo tissue morphology of various brain biopsies. Micrometer-scale OCT resolution (0.9×2 μm, axial×lateral) is achieved in biological tissue by interfacing a state-of-the-art laser Δλ=260 nm, and exfiber) to a free-space OCT system utilizing dynamic focusing. UHR OCT images are acquired from both healthy brain tissue and various types of brain tumors including fibrous, athypical, and transitional meningioma and ganglioglioma. A comparison of the tomograms with standard hematoxylin and eosin (H&E) stained histological sections of the imaged biopsies demonstrates the ability of UHR OCT to visualize and identify morphological features such as microcalcifications (>20 μm), enlarged nuclei of tumor cells (∼8 to 15 μm), small cysts, and blood vessels, which are characteristic of neuropathologies and normally absent in healthy brain tissue. © 2005 Society of Photo-Optical Instrumentation Engineers.