Poly(N-isopropylmethacrylamide)s (PNIPMAMs) have become commercially available as kinetic hydrate inhibitors (KHIs). PNIPMAMs are usually made by standard radical polymerization, which does not allow control over the polymer tacticity. We have now synthesized PNIPMAMs using stereospecific radical polymerization giving a fairly high degree of tacticity control. In this paper we present results on the performance of different tacticities in KHI tests with synthetic natural gas in stirred autoclaves and on tetrahydrofuran (THF) structure II hydrate crystal growth. The molecular weights of these polymers are almost the same. From the results, we can conclude the effect of polymer tacticity on the KHI performance of PNIPMAMs is noticeable but not very significant. PNIPMAMs with a higher syndiotactic percentage performed slightly better than PNIPMAMs with a lower syndiotactic percentage. Both polymers also gave a similar effect on the morphology of the THF hydrate crystals, indicating some kind of crystal surface adsorption. The PNIPMAMs investigated have a fairly high syndiotactic percentage. In fact, we found that it was difficult to make PNIPMAMs with less than 45% syndiotactic percentage, even using standard radical polymerization methods. This suggests that any method to make commercial NIPMAM-based polymer Kills via radical polymerization will necessarily give polymers with a fairly high percentage of syndiotacticity.