hydrazidicazidesrearrange to semicarbazides. In trifluoroacetic acid, both trifluoroacetyl semicarbazide and the parent semicarbazide are isolated, and the variation in yield with the nature of the hydrazidicazide has been investigated. We have also demonstrated, by use of an optically active hydrazidicazide substrate, that the migrating group in the aziderearrangement retains its configuration