The emission characteristics, e.g. energy spread, energy deficit, and M2+/ M+ ratios from Al, Ga, In, Bi and Au 90Si 10 liquid metal ion sources (LMIS) are discussed in terms of a field evaporation/postionization mechanism. It is shown that this model of LMIS is generally supported by the results. Focused beam results are presented which suggest a Gaussian source size for a Ga LMIS < 500 Å. It is shown that the best focused beam performance, i.e. maximum target current density for a specific beam size, is generally achieved at the lowest possible value of total current.