Kinetic hydrate inhibitors (KHIs) have been used successfully in the field for about the last 14 years to prevent gas hydrate formation Mostly in gas and oilfield production lines. They work by delaying the nucleation an(] often also the growth of gas hydrate crystals for periods of time dependent on the subcooling in the system. Poly(2-alkyl-2-oxazoline)s [or poly(N-acylalkylene imine)s] are a known class of KHI, but no work has Previously been published detailing a systematic study of structure versus performance. In this paper we report the KHI performance of poly(2-alkyl-2-oxazoline) homopolymers and statistical copolymers with alkyl side groups LIP to four carbon atoms. The study includes hydrate crystal growth tests on structure 11 tetrahydrofuran hydrate crystals as well as high pressure nucleation and crystal growth Studies on a synthetic natural gas mixture giving structure 11 hydrates. Seawater biodegradation Studies oil all the polymers according to the OECD306 procedure indicate that they are all poorly biodegradable (<20% in 28 days).