Ultrasonic three-dimensional images are constructed by “stacking” B-scan tomograms or ultrasonic CAT scans with a computer algorithm for subsequent perspective or sectional display. Perspective images of surfaces representing Doppler measurements of fluid velocity are illustrated in combination with isovelocity contours for flows through a flexible tube in vitro. Isospeed contours calculated from a dynamically moving epicardial surface are mapped onto the heart surface illustrating the combination of quantitative parametric data with a qualitative surface display. The efficacy of three-dimensional displays for increasing the information density and comprehensibility of pictoral representations of ultrasonic data sets is discussed.