The effect of limited exercise on pulpal blood flow was assessed by laser Doppler flowmetry (LDF). The primary aim of the investigation was to determine whether clinically significant changes could be induced by mild exercise when LDF was used to monitor pulpal blood flow. Blood flow readings were obtained from the coronal pulps of 17 upper central incisor teeth of 10 human volunteers before, during and after limited exercise. Readings were also obtained from the adjacent attached gingivae. Pulse rate was recorded concurrently. Pulpal blood flow was found to vary during exercise, with a mean percentage change of 38% from the level at rest; the range was from a 100% decrease to a 200% increase. The mean percentage increase in gingival blood flow was 65%, with a range of 6-300%. The main indication that blood flow was being assessed was the pulsatile nature of the output. Results were compared only within individual teeth. The pulse rate increased during exercise (mean percentage increase 54%, range 11-98%). There was no direct relationship between increased pulse rate and pulpal blood flow. It was evident that the mechanisms controlling pulpal and gingival blood flows differed. Laser Doppler flowmetry readings were only reproducible in individual teeth provided that the patient was at rest, and this should be taken into account in clinical or research measurements.