Abstract: In this pi ece of work, an attempt is made to gauge the effect of constantly declining fertility on population aging in Bangladesh through the application of an analytical model proposed by Ansley Coale (1972), which employs stable population theory. We have assumed a linear constant decline of fertility in Bangladesh to obtain NRR=1 by the year 2011. The projected age distribution of 2011 shows that the proportions of males and females 60+ will be 7.02 percent and 7.46 percent respectively. This means that there could be an increase of 18.98 percent and 55.4 percent in the proportion of males and females (60+) from 1991 to 2011. The median age of males increases from 17.65 to 26.27 years during the same period. For females, the increase is from 17.88 to 26.09 years.