The characteristics of a microcomputer-based system for measuring ventilatory parameters in neonates on mechanical ventilatory assistance are described. The tidal flows of the infant are sensed by a pneumotachometer housed in the wall of a constant pressure plethysmograph. The processed signal from the pneumotachometer is fed to a dedicated analog-to-digital converter and 6502 microcomputer, which, in turn, loads a dual ported RAM buffer with smoothed, digitized, tidal flow data. At the end of each minute the Apple 2+ processes the accumulated data and computes tidal volume, respiratory frequency, minute volume and the difference between inspired and expired volume. Numerical outputs for these variables and a histogram, representing the distribution of tidal volumes for the minute, are printed on a dot matrix printer. This inexpensive system is capable of presenting contemporary, summarized, ventilatory data in a form that is potentially very useful for the clinicians who are managing the care of the infant.