Probing of the sensitive, soft periodontal tissues differs markedly from probing of the dental hard tissues and caries. Periodontal probing requires special skills as well as an understanding of the tissues being examined, the probing procedure and the use of an appropriately designed instrument. Periodontal probing seeks to complement the initial visual assessment of the status of the periodontal tissue. It has multiple roles: to assess the haemorrhagic response to physical pressure; to determine the presence of aetiological factors such as calculus, defective dental restorations and root erosion, and to determine the pocket dimensions. It is also essential that the periodontal tissues should not be traumatised during probing. These defined aims of probing can only be achieved by use of an instrument that is capable of performing these functions, is designed to be 'tissue friendly', suitable as a measuring instrument, and standardised to ensure reproducibility, particularly with respect to the recommended pressure of 20 g exerted during probing. In addition, the ideal probe should be suitable for use both in the clinical setting where precise data documentation is required on an individual patient basis, and for screening purposes, as in epidemiology. A probe designed to achieve these attributes