Effects of zeolite pore structure on skeletal isomerization of 1-butenes are investigated. Three 10-member ring zeolites, ferrierite, ZSM-23, and ZSM-5, are studied and compared. Results show that ferrierite, with intersecting 10-MR and 8-MR channels, has better isomerization activity than ZSM-23, with monodirectional 10-MR channels, ZSM-5 with two intersecting 10-MR channels is not a selective isomerization catalyst.