AbstractThis paper reports data on the long term stability of the phosphorus-fluorine bond of sodium monofluorophosphate (MFP). Spontaneous hydrolysis of the drug in bulk form follows first order kinetics. Chemical stability, expressed as its t1/2, was found to differ with different MFP preparations (t1/2= 35 to 114 months). Chemical stability of MFP in tablets appears dependent upon the method employed in their preparation. The long term stability of aqueous solutions is affected, as expected, by pH and temperature.