Niagara Mohawk Power Corp., a subsidiary of National Grid plc (NYSE: NGG), announced that its Board of Directors has declared dividends at the following rates for all series of its preferred stock.

.85% of $100 par value on the 3.40% Series;

.90% of $100 par value on the 3.60% Series;

.975% of $100 par value on the 3.90% Series.

Preferred stock dividends are payable June 30, 2010, to holders of record June 7, 2010.

Niagara Mohawk Power Corp., doing business as National Grid, provides electricity service to approximately 1.5 million customers and natural gas service to approximately 565,000 customers in upstate New York. The company is based in Syracuse, N.Y. Its parent company also has electricity and gas distribution operations in New England.

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