The investment bank has plagued by legal worries since the Securities and Exchange Commission sued it in April, claiming it defrauded investors in a bubble-era subprime debt deal. But you’d never know it to look at the rankings of the most active underwriters.

Goldman  was the top underwriter of mergers-and-acquisition deals in the first half of 2010, Dealogic said, backing 78 announced deals worth $136 billion. The firm took in $353 million in estimated fees on the transactions, giving it a  Wall Street-leading 13% market share.

The performance vaulted Goldman to the top of the league tables, ahead of Morgan Stanley , which was No. 1 over the first half of last year. JPMorgan Chase was third both years.

Goldman also topped ThomsonReuters’ rankings of M&A action.

In underwriting stock deals, Goldman was second to JPMorgan, as it was last year. It took in $529 million in equity underwriting fees, Dealogic estimates. The firm said the first half of 2010 was the slowest for underwriters since 2005.

Goldman also gained in the rankings of banks arranging corporate buyout loans. There, the top performer both this year and last was Bank of America’s  Merrill Lynch, which served as a so-called bookrunner on $54 billion worth of deals accounting for a quarter of the market. JPMorgan was second, as last year, with 16% of the market.

Goldman ranked a lowly eighth, with just 3% of the market. But that’s a vast improvement over a year ago, when it placed 21^st.

Goldman shares, which have been trading near a 52-week low amid worries about the firm’s legal bills and its profit outlook in a regulatorily reformed world, rose 2% in early trading to $137.