Positive ions formed directly by excimer laser ablation in vacuum of several lanthanide (Ln) and transition metal solid materials-including Ln(2)O(3), Ln(2)S(3), LnF(3), Ta2O5, ZrO2, TiO, and TiO2-were identified by time-of-flight mass spectrometry. Variations in ion yields were investigated as a function of the composition of the precursor material, laser irradiance, and ion sampling delay after ablation. The compositions of the observed polyatomic ions reflected the distinctive chemistries of the metal constituents, but the ion yield distributions were not generally indicative of the particular chemical/valence constitution of the target material. For example, the yield of CeO+ relative to Ce+ was substantially greater from the trivalent cerium oxide, Ce-2(WO4)(3)(s), than from tetravalent CeO2(s). Observed ion distributions apparently reflected the chemical composition of the ablation plume and the degree of gas-phase recombination therein. The observed abundances of polyatomic ions were found to correlate well with their estimated bond strengths. Further obscuring the chemical composition of the progenitor, minor changes in ablation, and sampling parameters-especially irradiance and sampling delay-were often manifested as significant variations in relative ion intensities.