Previously, under the Representation Act, 1996 Ontario was divided into electoral districts whose names and boundaries were identical to those of its federal electoral districts, and required redistribution whenever a readjustment took place at the federal level under the Electoral Boundaries Readjustment Act (Canada).

With the passing of Bill 214 and the Representation Act, 2005, Ontario’s electoral boundaries will no longer be identical to the federal electoral boundaries. Beginning with the next provincial general election on October 4, 2007, Ontario will be divided into 107 electoral districts. The districts will consist of 11 northern electoral districts that are identical (except for a minor boundary adjustment) to the ones that existed on October 2, 2003, and 96 southern electoral districts that are identical to their federal counterparts, as they existed on September 1, 2004.

The 11 northern electoral districts are: Algoma—Manitoulin, Kenora—Rainy River, Nickel Belt, Nipissing, Parry Sound—Muskoka, Sault Ste. Marie, Sudbury, Thunder Bay—Atikokan, Thunder Bay—Superior North, Timiskaming—Cochrane, and Timmins—James Bay.

The new electoral boundaries will remain until they are replaced by new legislation. Any changes to the names of southern electoral districts that may be made at the federal level after September 1, 2004 are also adopted at the provincial level, but only if the boundaries of the electoral district are unchanged.