The thermal electrocyclic ring closure of (2E,7E)-3,4,7-trialkylnona-2,4,5,7-tetraenes (divinyl-4,5-allenes) is regioselective, occurring at the most sterically congested vinylallene subunit to afford the trisubstituted alkylidenecyclobutene. Ring closure of both divinylallenes and vinylallenes displays high torquoselectivity (exclusive formation of the (E)-alkylidenecyclobutenes) when the substituent at C4 is a sterically demanding alkyl group and the substituent at C2 is a formyl group. Ab initio calculations clearly demonstrate the dominant steric influence of the bulky C4 substituent in these selectivities. However, torquoselectivity appears to be enhanced if cyclization involves loss of conjugation by a π system encompassing the C2 substituent.