With the succesful national family planning program and rapid socio-economic advancement since 1962, the contraceptive prevalence rate has risen from 9 percent in 1964 to 79 persent in 1991, with the corresponding total fertility rate(TFR) going from 6.0 in 1960 to 1.6 in 1988 which is considerably below the replacement fertility rate. The main purpose of this study is therefore, to identify the structural and causal factors that contributed to the fall in fertility over the last three decades, in an effort to formulate future population policy directions and strategies.