Using the semiempirical computational method AM1 we have computed the enthalpies of ionization of enols1–21and correlated these values with solution and estimated pKa's. From this initial study it appears that, in general, it is possible to predict the pK's of acyclic enols within ± 1 pKaunit. On the basis of this correlation we predict the pKa's of 1-hydroxy-1,3-butadiene (3-butenal enol) (9.7) and 1,1-difluoroacetone enol (9.6) and suggest that the previously estimated pKaof 1,1-dichloroacetone enol (6.2) is low by approximately 3 pK units. We find computationally (this has been established experimentally) that theZ-enol of phenylacetaldehyde is less acidic than theE-enol.Keywords: enols, acidities, computational studies, AM1.