The morphology and growth characteristics of alpha-Si3N4 whiskers grown by pyrolysis of amorphous Si-N-C powders were investigated mainly by TEM. It was found that the whiskers exhibited various morphologies including ribbon-, rod-, prism- and nodule-like whiskers. Three growth directions were found : {<1(1)over bar 00>}*, {1010}*, and {0001}* which are dense planes in the hexahedral structure of alpha-Si3N4. No bobbles existed on the whisker tips, but there was a leading growth along the whisker long axial directions and small Si3N4 grains bonded on the whisker tips, which indicated that the whiskers nucleated on small alpha-Si3N4 grains and grew by a vapour-solid condensation mechanism.