The first tandem autotransformations of heteroaromatic carbenes have been found. These reactions involve cleavage of the 1-tert-butyl-3,4-diaryl-1,2,4-triazol-5-ylidenes 1a-d to form benzonitriles and the respective carbodiimides, followed by further reactions of the latter with carbenes 1a-d to afford the 3,4-diaryl-5-(1-tert-butyl-3-arylamidin-2-yl)-1,2,4-triazoles 5a-d. The X-ray structures of the carbene 1-tert-butyl-3-phenyl-4-n-bromophenyl-1,2,4-triazol-5- ylidene (1a) and the amidinotriazole 3-phenyl-4-p-bromophenyl-5-(1-tert-butyl-3-p- bromophenylamidin-2-yl)-1,2,4-triazole (5a) were determined. The reactions of 1a with the electrophiles diphenylcarbodiimide, acetonitrile, and diphenyldiazomethane are also described.