Rapidly solidified (R.S.) Ni50-xTi50Cox ribbons have been produced by a single roller melt spinning technique. The influence of rapid solidification experimental parameters on the structure and transition behaviour were investigated by DSC, by X-ray diffraction and by TEM. The DSC curves are stable from the first cycle and a preferred orientation exists in the rapidly solidified NiTiCo alloys. An experimental parameter such as quenching temperature increasing is followed by the precipitate growth. These precipitates of Ti2Ni, may be responsible for the martensitic and R transition temperature decreasing. Annealings enlarge the precipitate size and the transition temperatures decrease again.