The Knoevenagel condensation of malononitrile with various arylaldehydes was studied as an uncatalyzed reaction at ambient temperature. This study was prompted after discovering that a reaction mixture left standing for extended times after mechanochemical treatment would continue to react to significantly higher yields. We report that a mixture (solid/solid or solid/liquid) of reactants converts in some cases quantitatively to the target product in the absence of any solvent at room temperature. The yields can be increased if the mixture of reactants is seeded with the target product. It is also possible to carry out the condensation reaction in solution at room temperature without any stirring. Depending on the aldehyde and the polarity of the solvent yields can be quantitative as well.