Kinetic hydrate inhibitors (Kills) are water-soluble polymers that have been used for almost 20 years as a method to prevent the formation of gas hydrate plugs. Most classes of Kill polymers contain amide groups. We have now found a simple route to synthesize poly(N-vinylalkanamide)s (PVamides) from polyvinylamine. In this paper, we present results on the KHI performance of PVamides with varying alkyl chain lengths in the side group. This has been performed in tests with a structure-II-forming synthetic natural gas in high-pressure rocker cells and on tetrahydrofuran (THF) structure II hydrate crystal growth. The Kill performance of poly(N-isopropylacrylamide)s (PNIPAMs) and poly(N-vinylisobutyramide)s (PNVIBAs) at varying molecular weights was also compared, because these two polymers differ only in the orientation of the amide group.