A master alloy with eutectic compositions of Ni-30.26Mo-6.08Al-1.43 V (wt%) has been directionally solidified (DS) into gamma/gamma’-alpha alloy. The microstructural as-ageing treatment was studied by means of high resolution electron microscopy (HREM). A majority of alpha fibres still display the Bain orientation relationship with the gamma’/gamma matrix. In a few cases, however, the so-called Nishiyama-Wasserman (NW) orientation relationship is found in specimens aged at 850 degrees C for 2000 h. Different microdomain structures of the gamma phase, corresponding to different ageing temperatures, were revealed. Orthorhombic Ni3Mo phase, with a size of tens of nanometres, was found to precipitate inside alpha fibres after ageing at both 850 and 650 degrees C. Occasionally, an gamma’-Ni3Al phase with lamellar twin structure was also found to coexist with Ni3Mo precipitate inside the alpha fibres. The orientation relationships between the precipitates and the alpha fibres were determined. Energy dispersive X-ray analysis (EDX) showed that the precipitation of Ni3Mo and Ni3Al is due to solid solution of Ni and Al in the alpha fibres.