Oligo- and poly(ferrocenylene alkylene)s, [Fe(C5H5-x)(C5H5-y)CHR](n) (x=y=1 or x=2, y=0; R=alkyl, aryl), were synthesized by Lewis acid-promoted addition-condensation polymerization of ferrocene with aldehydes. The reaction of alkyl aldehydes, such as n-hept-CHO, EtCHO and nBuCHO, with ferrocene yields a mixture of the cyclic and linear poly(ferrocenylene alkylene)s, while aryl aldehyde, such as C6F5CHO, CF3C6H4-4-CHO and MeC6H4-4-CHO, forms the linear polymers exclusively. The linear polymer has terminal Fe(C5H4)(C5H5) and CH(2)Aryl groups, which are characterized by high resolution mass spectroscopy. Results of addition-condensation polymerization of ferrocenemethanol catalyzed by BF3 indicate that the propagating polymer of the above addition-condensation polymerization contains terminal 1-hydroxyalkyl-ferrocenylene group, Fe(C5H4)[C5H4{CH(OH)R}]. The trimer prepared from ferrocene and paraformaldehyde dimethylacetal contains 1,1-, 1,2-, and 1,3-ferrocenylene units, suggesting that the polymers obtained from alkyl and aryl aldehydes are also composed of these structural units. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3627-3635