New cyclophosphazene derivatives incorporating five different mesogenic moieties have been synthesized and their liquid crystalline behaviour has been studied by DSC and polarizing optical microscopy. Smectic A and unclassified smectic 1 phases have been found for the first time in these cyclotriphosphazene derivatives. The relatively good thermal stability of the smectic phases of the mesomorphic cyclotriphosphazenes was interpreted in terms of the peculiar molecular shape of the cyclotriphosphazenes.