As the Kyoto target set for Canada is to reduce GHG emission by 6% of the 1990 level by 2008-2012, several options are being considered to achieve this target. One of the possible options in Ontario is geological sequestration of captured CO2 in saline aquifers, where CO2 is expected to be stored for long geological periods, from 100 to several thousand years depending on the size, property and location of the reservoir. The preferred concept is to inject CO2 into a porous and permeable reservoir covered with a cap rock located at least 800 in beneath the earth's surface where CO2 can be stored under supercritical conditions. This paper evaluates the capital and operating cost for CO2 sequestration in southwestern Ontario from a 500 MW coal fired power plant. The main focus is on the cost of sequestration (CO2 transport and injection), and thus, the cost of capturing and pressurizing the CO2 from the plant flue gas is not considered here. A significant amount of capital investment is necessary to transfer CO2 from a 500 MW fossil fuel power plant to the injection location and to store it underground. Major components of the cost include: cost of pipeline, cost of drilling injection wells and installing platforms, since the more plausible injection area is under Lake Erie. Many uncertainties are associated with cost estimation; several are identified and their impacts are considered in this paper. The estimated cost of sequestration of 14,000 ton/day Of CO2 at approximately 110 bar in southwestern Ontario is between 7.5 and 14 US$/ton Of CO2 stored. (C) 2004 Elsevier Ltd. All rights reserved.