In operating a three‐level maser one wishes to know the external magnetic field and crystal orientation necessary to match a given pair of frequencies. In the case of Cr+++a fourth‐degree secular equation determines four energy levels for each value of external fieldHand crystal orientation &thgr;. Determination of the latter two variables, given two desired frequencies of operation, ordinarily involves either the solution of a tremendous number of fourth‐degree equations and extrapolation towards the required solution, or determination of the matching conditions by experimental methods. In the following a method is described, allowing direct calculation ofHand &thgr; for a three‐level ruby maser.