The main trends in the use of the quasi-monochromaticity method in field-ion microscopy are considered, as well as the existing means of its practical realization for the separation of the investigated phenomena. Certain difficulties of the method are considered. New trends in the application of the method are reported, particularly for the investigation of the kinetics of continuous field evaporation, for the study of the initial stage of image formation in the field-ion microscope, in the analysis of surface particles, and others.