During the past two decades, improvements in the resolution and reliability of instrumentation and techniques have allowed A- and B-scan ultrasonography to join direct visualization, fluorescein angiography, and radioactive phosphorus testing as primary diagnostic modalities in the evaluation of intraocular neoplasms. Because overlying opacities have no effect on the examining ultrasonographic frequencies, ultrasound has the unique ability to depict the nature of intraocular pathology when the media are optically opaque. Physics, history, instrumentation and techniques are described, and criteria for diagnosis of uveal malignant melanomas by standardized A-scan and B-scan methods are discussed and illustrated.