Electron ionization and chemical ionization mass spectra of acetates of lithium, sodium, and potassium and mixtures of these compounds have been measured with sample introduction via a direct exposure probe. The distributions of positive and negative cluster ions of these metal (M) acetates (OAc) extend to unexpectedly high masses. In the negative ion mode, the intensities of cluster ions [M(n)(OAc)n+1]- follow an exponential decay with increasing mass. However, the intensity of [M2(OAc)3]- reproducibly falls below the exponential curve. Collision-induced dissociation MS/MS spectra for several negatively charged cluster ions formed lithium acetate show simple losses of acetate anions and neutral molecules.