The 1978 Constitution of Sri Lanka provides for the election of members of Parliament from 22 multi-member electoral districts through the proportional representation electoral system.
All but two of the electoral districts are conterminous with their namesake administrative district. The two exceptions are Jaffna (which covers the administrative districts of Jaffna and Kilinochchi) and Vanni (which covers the administrative districts of Mannar, Mullaitivu and Vavuniya). The first general election which used these electoral districts was in 1989.
According to the constitution the Parliament should consist of 225 seats (members):
The constitution required the establishment of a delimitation commission for the delimitation of the electoral districts and apportion the 36 provincial seats. The constitution limited the number of electoral districts to between 20 and 25.
The Delimitation Commission was appointed on 29 November 1978. Its decision was published on 15 January 1981. The country was divided into 22 electoral districts. 21 of the 22 electoral districts were conterminous with their namesake administrative district. The other electoral district - Vanni - consisted of the administrative districts of Mannar, Mullaitivu and Vavuniya. The 36 provincial seats were apportioned as follows: