The popular misconception that sustained fertility at replacement level is necessary to prevent long-run population decline needs to be dispelled. Fertility is currently below replacement level in all the More Developed Countries, except Israel. 65% of these countries also have positive net immigration, with the exceptions mostly being in Eastern Europe. Any population with constant below-replacement fertility, constant net migration numbers, and constant mortality over time will approach a stationary state, with constant numbers at all ages. The size of the asymptotic stationary population may be seen as an intrinsic measure of the very long run population growth implication of the combination of fertility, mortality and migration for a population and time period. For eight European migrant-receiving countries plus Australia and Canada, this paper calculates the long-run population size implications of current fertility, mortality and net migration, and the level of fertility which would be needed to achieve a long-run population equal the current population if the country were to maintain its currently-prevailing levels of immigration and mortality. Preliminary results based on 2006-10 data show very wide variation between countries. For example, Hungary’s population would fall to 24% of its current size, whereas Australia’s population would increase more than tenfold. Total Fertility Rates which equate long run and current population sizes range from 0.81 for Australia to 1.9 for Hungary. For five countries reductions in fertility below the current level would be needed to equate the long run population with the current size. The sensitivity of the results to variation in immigration is discussed. I suggest the adoption by demographers of this paper's method of benchmarking of fertility against a level which is consistent with zero long-run population growth under continuation of current migration patterns, could help to prevent misconceived setting of national goals for fertility (e.g. Australia's).