A new periodontal probing system has been developed which incorporates the advantages of constant probing force, precise electronic measurement to 0.1 mm and computer storage of the data. The system includes a probe handpiece, displacement transducer with digital readout, foot switch, computer interface and personal computer. A unique movable arm design enables the probe handpiece to maintain smooth operation and makes it easy to clean and sterilize. Electronic recording of the data (actuated by pressing a foot switch) eliminates errors which occur when probe tip markings are read visually and the data are called to an assistant. Computer storage and analysis of the data facilitates detecting changes in pocket depth and attachment level by rapidly comparing data recorded at different visits. The system was evaluated in 3 experiments using a 0.4 mm diameter tip and a 25 g probing force. The standard deviation of repeated pocket depth measurement was less (0.58 mm versus 0.82 mm) than that of a common probe. With paired readings referenced to an occlusal stent, the standard deviation of repeated attachment level measurements was 0.28 mm. A loss of attachment level was detected to a certainty of 99% with less than a 1 mm change. This is a significant improvement over common probes, which require a 2-3 mm change for equivalent positive identification of change in attachment level.