The polymerizations of ethyl vinyl ether, n-butyl vinyl ether and isobutyl vinyl ether were investigated with a series of pyridine bis(imine) complexes of iron(II) and cobalt(II) in the presence of methylaluminoxane. The cobalt catalysts showed much higher activity and produced higher molecular weight polymers than their iron analogues. Both catalyst systems produced predominantly atactic polymers. There were no specific trends in the activity and the polymer molecular weight, according to the steric bulk around the metal center.