The interpretation of two‐dimensional radiographs or computerized tomography (CT) or ultrasound (US) sections with inferences made about three‐dimensional anatomy is the foundation of diagnostic radiology. A large variety of estimation methods which can be applied to two‐dimensional CT/US sections to estimate their three‐dimensional properties is presented. The techniques are easily utilized in a research or clinical setting, do not require computerization, and can provide statistically accurate three‐dimensional information based on two‐dimensional sampling with a minimum of effort. Although the examples are directed at diagnostic radiology, the estimation procedures may be employed in analogous fields such as microscopy or section anatomy.