Whether such individuals have different gingival blood flow and temperature responses to local cooling than age- and sex-matched healthy controls was tested. Ten patients with a history of localized juvenile periodontitis or rapidly progressive periodontitis were selected from a periodontal clinic and matched with healthy controls. Gingival blood flow and temperature were monitored continuously before and after cooling via a twin probe placed in the gingival sulcus on the buccal of tooth No. 26. Blood flow was assessed by laser Doppler flowmetry and temperature by a small metal thermistor. Resting values were first recorded for 5 min, followed by 3 min of cooling to 19 degrees C by a gentle stream of cool air, then 12 min of rewarming was allowed. This protocol was repeated twice. Blood flow changes were analysed as the slope of the line formed between the last 2 min of cooling and the last 2 min of rewarming; temperature curves were analysed by a least-squares curve fit of a bi-exponential function. Patients with localized juvenile periodontitis and rapidly progressive periodontitis had similar rewarming temperature curves, but significantly faster blood flow recovery curves than controls (p less than 0.03). Thus, gingival blood flow in young periodontitis patients recovered more rapidly after local cooling than in healthy controls.