A clinical evaluation of the XPERT NCT (Reichert Ophthalmic Instruments) applanation non-contact tonometer was conducted at the Baltimore VA Medical Center. Each of 620 eyes were measured by the XPERT and then by one of seven operators of varied experience, each using one of four calibrated Goldmann applanation tonometers (GATs). Measured pressures ranged from 1 to more than 60 mmHg. The interval between XPERT and GAT measurements varied from a few minutes to almost 1 hour. Despite the increased potential variability of our protocol, the XPERT agreed very closely with GAT. Population IOP means agreed within 0.3 mmHg; regression coefficients defining XPERT's calibration, relative to GAT, were slope (m) = 1.025, and Y intercept (b) = 0.7 mmHg. The standard deviation of matched pair differences, was Sd = 2.7 mmHg. We conclude that the XPERT NCT is a highly accurate and reliable instrument. Our experience showed it to be convenient and well accepted by staff and patients. It proved faster, easier to use, and its "air-puff" is quieter and less intense than NCT I and II. In the companion paper, we examined the reliability of GAT used as a clinical comparison reference in evaluating the XPERT.