NiTi alloys with equiatomic composition of NiTi have the highest technological interest for its potencial application in differents areas such as biomedical, naval, aerospace, nuclear, automobilist , robotic,etc. In this work , it was used a 50Ni50Ti at % powder mixture, comercially pure, prepared by mechanical alloying in a Attritor with the following conditions: the milling speed and the ball charge were 1500 rpm and 10:1 respectively. The milling time was 2,4,8 and 16h, under an argon atmosphere at room temperature. After milling it was determined the particle size distribution, the phases by X-ray diffractions (XRD) and the powder morphology by scanning electron microscopy (SEM). The milling promotes dissolution of Titanium in Nickel and continuous amorphization by increasing the milling time. After 16h milling the alloy was almost amorphous. The powders after milling were compacted and heat treated at high temperature and microstructural evolution was characterized. In the heat treated samples were detected different phases showing heterogeneity in the alloy. The detected phases were Ni3Ti, NiTi, Ni2Ti and Ni2Ti4O. Contamination by milling was detected in the powder after milling and in the heat treated samples.