The quantitative analyses and other applications described in this article indicate a useful future for the ion-microprobe mass analyzer in many areas of the science of solid materials. It should be possible to analyze all the elements quantitatively, but detection sensitivities will vary depending on the matrix, the element, and the polarity of the sputtered ion being studied. Most elements will have optimum yields in the spectrum of positive sputtered ions, and will be detected in concentrations of parts per million in micrometer-sized sampling areas. Electronegative elements will be detected with similar sensitivities in the spectrum of negative sputtered ions, but inert gases, which are ionized with difficulty and have small electron affinities, will be detected with considerably poorer sensitivities. In general, it will be possible to measure isotope ratios without chemical separation of the constituent elements of the sample. The precision of an ion microprobe isotope ratio measurement depends basically on the counting rates involved, and its accuracy can approach its precision if auxiliary standards are used. The isotope ratios of different elements can be compared readily because of the small mass-discrimination effects of the system. Surface layers can be quantitatively analyzed in depth with a resolution of tens of angstroms; hence, it should be possible to study the migration of atoms.