Certain trans-6-[[(substituted)pyridin-3-yl]-alkyl- and alkenyl]tetrahydro-4-hydroxypyran-2-ones and the corresponding ring-opened acids derived therefrom are potent inhibitors of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase) and are useful as hypocholesterolemic and hypolipidemic agents.