The addition of dichlorocarbene to cyclopropene has been studied with direct dynamics quasiclassical trajectories using B3LYP/6-31G*. The trajectories yielded 1,1-dichlorobicyclo[1.1.0]butane and 1,1-dichloro-1,3-butadiene in a ratio of 4.7:1, which is consistent with the experimental ratio of 4:1. The large majority of trajectories formed products within 100 fs of the start of the trajectory and proceeded in a concerted manner to the bicyclobutane or butadiene; no zwitterion or biradical intermediate was observed. Eight trajectories generated bicyclobutane and subsequently dissociated chloride to form an ion pair, which recombined to form 2,3-dichlorocyclobutene. The lifetime of the ion pair averaged 95 fs, which was too short to be considered an intermediate, consistent with previous calculations that characterized the ion pair as a transition state. This study lends strong support to the previous proposition that the addition of CCl2 to cyclopropene is controlled by dynamic effects. Copyright © 2011 John Wiley & Sons, Ltd.