A review of existing approaches to the estimation of wanted fertility concludes that these measures typically contain an upward bias. An alternative methodology is therefore proposed to estimate wanted fertility from survey questions about women's desire to continue childbearing. This new methodology is applied to data from 48 surveys in developing countries. The results from this exercise indicate that in these populations on average 26 percent of fertility is unwanted, which is substantially more than estimates derived with other methods. The proportion unwanted apparently varies systematically over the course of the fertility transition: it is lowest at the beginning and end and highest among countries in mid-transition.