The problem of selection in the prediction of the effective size of population under nonrandom mating with different numbers of male and female parents was considered. Following the variance of change in gene frequency approach, an expression was derived. A comparison was made between the equation presented by Santiago and Caballero (1995) and that obtained in the present study. It was found that some important terms arising from selection are neglected in the equation of Santiago and Caballero (1995).