Specimens of Ni-25 at.% Cr alloy were heated for 60 min at different temperatures ranging from 600 to 1000 degreesC, quenched in brine and then aged isochronally at temperatures ranging from 150 to 650 degreesC for 30 min and aged isothermally at 70 and 400 degreesC for various times. It is observed that the resistivity rises up to a saturation value on aging isothermally at 400 degreesC. The initial increase in resistivity during aging may be described by the clustering of solute atoms at the early stages of precipitation that may transform to stable precipitates for very long aging times. The sudden variation in resistivity with rising temperature may be attributed to the onset of the CrNi3 ordering reaction. (C) 2002 Elsevier Science B.V. All rights reserved.