Vinylformamide (VFA) is cationically polymerized in various solvents at 273 K and 253 K reaction temperature by the following initiators: iodine, bis(4-methoxyphenyl)-methyl chloride/silica, triphenylmethyl chloride/silica, and trimethylsilyl triflate. In every case defined oligomers with narrow molecular weight distribution are obtained in moderate yield (20-50%). Acid hydrolysis of the obtained oligomers yields well defined oligovinylamine products. The cationic initiation mechanism of VFA is discussed in terms of the HSAB-concept(a).