The purpose of this study was to evaluate the effect of a 4-minute application of intrusive orthodontic force on human pulpal blood flow (PBF) with laser-Doppler flowmetry. Eight subjects had an intrusive force applied to a maxillary central incisor through a lever system. A cast chrome-cobalt coping was fabricated to fit over the incisor of each subject, and thus provided a reproducible point of force application as well as stabilization for the laser-Doppler flowmetry probe. Each subject participated in five testing sessions. During each session, PBF was measured during a 4-minute baseline period, then during the 4-minute force application, and then for a 12-minute period after removal of the force. Weights of 0, 5, 50, or 500 gm were attached to the end of the lever to produce intrusive forces ranging from 75 to 4498 gm. During the fifth testing session, local anesthetic with vasoconstrictor (epinephrine 1:100,000) was administered in place of the force application to determine the ability of this experimental paradigm to detect reductions in PBF. Baseline PBF values did not differ among sessions. Force levels had no statistically significant effect on PBF. However, PBF did drop significantly after administration of the vasoconstrictor. These results suggest that PBF is not altered during the application of a brief intrusive orthodontic force.