Thermogravimetry with evolved gas analysis by infrared spectrometry was used to study the thermal degradation of thiophene fulgamic acid in an inert atmosphere. Contrary to the expectation that the amic acid would eliminate water to the corresponding imide, anomalous behaviour was observed whereby the compound lost ammonia. Control experiments on the thermal degradation of thiophene fulgide indicated an initial loss of a nitrile containing species. This might be attributed to the degradation of a trace impurity of dicyclohexylurea to form cyclohexylisocyanate. A proposal that dicyclohexylcarbodiimide (DCC) might have been present as an impurity was discounted on the basis of a measurement which showed that the DCC simply sublimed without formation of other decomposition products. Comparison of the results obtained from different experiments showed that the decomposition of thiophene fulgamic acid was more complex than simple ammonia loss followed by sublimation of the anticipated thiophene fulgide residue. Possible reasons for this are discussed.