Department of Chemistry, Lady Keane College, Shillong·793 001 Manuscript received 28 January 1992 revised 25 September 1992, accepted 29 October 1992 Ethyl 5-cyano-1,6-dihydro-6-oxo-3-pyridine carboxylates are recently reported compounds which exhibit cardiotonic activities. Ab initio MO calculations at the STO-3G level on the molecular geometries of three (methyl, Isopropyl and tert butyl) 2-substituted analogus of these compounds are reported. The preferred positions in the calculated energy surfaces are compared with their crystal geometries. The results indicate that the substitution pattern at the 2-position is primarily responsible for the cardiotonic potencies of these compounds.