The lawyers at Osler Hoskin & Harcourt haven't just been defending Magna International Inc.'s controversial payout for Frank Stronach before the Ontario Securities Commission. They have been doing big deals.

According to the latest Thomson Reuters rankings, Osler had the most Canadian merger and acquisition business in the first half of 2010, measured by the dollar value of announced deals. It advised on transactions worth $18-billion (U.S.), cornering 27 per cent of the market. Blake Cassels & Graydon and Davies Ward Phillips & Vineberg round out the Canadian law firms in the top five.

Top five law firms on announced deals with Canadian involvement in first half of 2010

1. Osler Hoskin & Harcourt $18.05-billion, 34 deals

2. Blake Cassels & Graydon $14.46-billion, 43 deals

3. Cravath Swaine & Moore $7.49-billion, three deals

4. Davies Ward Phillips & Vineberg $6.58-billion, 18 deals

5. Debevoise & Plimpton $6.04-billion, four deals

Source: Thomson Reuters