An analytical means of determining the low-frequency combustion stability for catalytic monopropellant thrusters has been presented. The use of frequency-analysis from feedback control systems is shown to predict the conditions of stable-unstable operation of a 2001bf hydrazine thruster. The open-loop transfer function for system response was obtained from the feedline and thruster equations for a pressure-fed, flexibly mounted thruster. The resulting set of six equations in six unknowns was normalized using the steady-state mass rate and chamber pressure. The open-loop character of the linearized, transformed equations was obtained from a stability analysis digital computer program. Experimental stable-unstable operation of a 2001bf hydrazine thruster was correlated by a 12 msec value of combustion time delay determined from the analysis. The analytical value of combustion time delay was shown to be in good agreement with experimental values determined by the method of flow-interruption. A simpler solution for a rigidly mounted thruster is also presented which allows rapid graphical determination of combustion stability.