Two basic approaches to diminish the explosivity of AN have been suggested: dilution of ammonium nitrate (AN) with a chemically inert material or incorporation of small amounts of material which increases the chemical reaction zone [Method of Desensitizing AN and the Product Obtained, United States Patent Office, No. 3,366,468 (1968); Fertilizer additives: can AN be defanged? C&E News (1995) 6]. While small-scale tests of these "deterred" AN formulations appeared promising, larger amounts (30 pounds under confinement) were found to be detonable, though with reduced performance [Institute of Makers of Explosives Report, 1995]. In this study thermal analysis was used to screen a large number of AN formulations in search of possible deterrents. The sodium. potassium, ammonium and calcium salts of sulfate. phosphate. or carbonate as well as certain high-nitrogen organics (urea, oxalate, formate, guanidinum salts) were chosen because they should enhance AN thermal stability and because they could be used with agricultural products. This study considers whether laboratory tests can be used as benchmarks in evaluating explosivity.