Using 18.7 million as the population size in 2001, an addition of 2.4 million is expected in the next three decades possibly creating numerous demographic, social, economic, environmental and cultural shifts in Sri Lankan society. Therefore population projections are of critical importance in the socio-economic planning process. Development activities which include population projections and data into the planning could have a higher success rate due to the level of preparation included in project planning. This study assesses the plausible demographic situations of a country through an understanding of the processes that may lead to a particular scenario in the future, whilst also highlighting expected implications of these scenarios. This paper also serves as a useful tool for users of these projections in discussing the extent of departures from the actual turn-out and indicating the record accuracy of previous projections that have been made for Sri Lanka.