Three periodontal probes - a manual probe and two computerized, pressure-sensitive probes - were studied to determine their relative recording accuracy. In the first part of the study, replicate probing measurements were taken with the three probes at shallow (less than 5 mm) and deeper (greater than or equal to 5 mm) periodontal sites. In the second part of the study, probing depths were determined on all teeth except third molars by the three probing techniques at a single appointment. Mean values between replicate probings for each instrument did not differ statistically, except for duplicate measurements with one of the electronic probes in pockets with depths greater than 5 mm. All three probes demonstrated higher standard deviations with increasing depth, which indicates decreased reproducibility of probing depth measurements. Results of this study suggest that an electronic, pressure-sensitive probe yields more reproducible probing depth measurements than a conventional manual periodontal probe.