An automated limb blood flow plethysmograph has been developed and interfaced to a PDP-11/60 computer. This system automatically inflates blood pressure cuffs, calibrates strain gauges, provides real-time display of limb circumference changes, and provides digital output of limb blood flow and real-time graphic display of cuff pressure. The system has been designed to require a minimum amount of user interaction by providing automatic calibration in situ, which is initiated by depressing a switch, and automatic venous cuff inflation, which initiates computer analysis of blood flow data. Digital and graphic display of blood flow is provided on a computer terminal 12 s after the start of venous occlusion. All raw data are stored on a disk for optional postexperiment analysis, which enables each blood flow curve to be graphically displayed and reanalyzed under user control. Calculated data are stored on a disk for output to a line printer at the conclusion of an experiment. A trend plot of all analyzed blood flows can be displayed on a computer terminal anytime during an experiment.