Serrated flow in a nickel-base superalloy was investigated in three microstructural conditions from room temperature to 973 K by tensile loading at strain rate of 6.5 x 10^-5 s^-1. Serrated flow was noticed for all temperatures above 473 K for solution-annealed microstructure, while no serrations were seen for aged microstructures above 823 K. Niobium depletion in the matrix as a result of precipitation was found to be responsible for the absence of serrations above 823 K in aged microstructures.