The stereoselectivity of the cycloadditions of 2-(D)methylidene-3-methylidenebicyclo[2.2.1]heptane (4) to various dienophiles has been determined. The exo- vs.endo-face selectivity depends on the type of dienophiles, and for olefinic ones, on the mode of attack (Alder- vs.anti-Alder endo rule). It is > 9:1 with N-phenyltriazolinedione (NPTAD) and ethylenetetracarbonitrile (TCNE), < 1:9 with dimethyl