Although the idea of using a satellite as a source of data for settlement studies is not new, actual measurements of the areal extent of settlements on a large scale has been meagre. A digital analytical approach has been used to identify and measure the areal extent of settlements in the Oyo-Ogbomoso-Ilorin area of Nigeria. Using 95 sampled pixels selected from Ilorin, Ogbomoso and Oyo as training areas, an area of about 249 km2has been classified as settlements. It was observed that settlements with built-up areas of about 300 h were identifiable from Landsat. Despite this observation, there is a need for further research to determine the level of accuracy of settlement identification and areal measurements which is possible from Landsat MSS data. The procedure of selecting subscenes to define known settlements is suggested as being a more accurate way of measuring the areal extent of settlements.