An investigation was carried out at the University of Agricultural Sciences. G.K.V.K. Campus. Bangalore, India, to determine the possible limits to parental divergence for the occurrence of heterosis in sunflower. Seven inbred lines were used to synthesize twenty-eight hybrids following diallel mating design. The magnitude of heterosis in these crosses and the magnitude of the divergence between the parents of the corresponding crosses were estimated. The study revealed sufficient evidence for the limits to the parental divergence to realize high frequency of heterotic crosses with high magnitude. Chances of occurrence of heterosis are higher when the parents are chosen to have their divergence between (m-s) and (m+s) compared with the crosses between the parents whose divergence fall outside this limit. The study also indicated a poor correspondence between the magnitude of heterosis and the genetic divergence.