The study attempts to explain changes in reproductive behaviour of rural women of Bangladesh that has occurred at a time when the country was predominantly poor and agricultural. Three different areas were studied, using time series analysis, and changes measured by demand for additional children and current contraceptive use. The findings show that demand for no additional children was generated prior to the fertility decline and that the family planning programme helped to mitigate the demand for fertility control modifying supply logistics since the late 1970s. Reproductive behaviour of women is strongly affected by biosocial and cultural factors related to patriarchal social structure. Desired family size in all three areas were similar prior to the fertility decline of the 1980s. It was lower than the fertility rate and is probably affected by prior improved survivorship. During the period studied, desired family size reduced equally in all three areas. With this same level of desired family size, an efficient Matlab Family planning programme successfully reduced fertility from the mid 1970s, while high fertility in the other two areas began to decline from the 1980s.