The aim of this study was to examine if laser Doppler flowmetry (LDF) could aid in distinguishing teeth with necrotic pulps from vital teeth and if so, which configuration of 5 experimental probes would give the best results. Each probe had 3 fibers arranged in a triangle. One fiber carried the laser light to the pulp tissue and 2 fibers carried the back-scattered light to the detector giving the output signal. The distance between the 3 fibers in the triangular arrangement in each probe was 250, 500, 800, 1000, and 1500 microns. A special rubber-base splint was used to hold the probe in place on the buccal surface of the tested teeth. Eleven anterior teeth with clinically diagnosed necrotic pulp were measured with the LDF method and the results compared to contralateral teeth with vital pulp. For the sake of comparison, 10 pairs of anterior teeth with vital pulps in 10 patients were tested as well. The LDF signals were fed into an analog printer and a lap-top computer where all calculations were done. With the LDF method, the output signals from the teeth with necrotic pulps were significantly lower with all 5 probes than the output signals from the contralateral vital teeth. On average, the signal was 42.7% lower from the teeth with necrotic pulps than from the vital teeth. Four of 11 teeth with necrotic pulp gave a positive response to an electrical pulp tester (EPT). The results suggested that the probe with the smallest separation of fibers was the most sensitive in distinguishing necrotic pulps from vital ones.