David Corkins is turning around Janus Capital Group Inc.'s flagship mutual fund and beating the returns of his biggest competitors at Fidelity Investments, American Funds, the Vanguard Group Inc., and Legg Mason Inc.

Corkins, who took over the $12 billion Janus Fund 15 months ago, reduced the number of stocks he invests in by a third, sold the worst performers, and invested in companies with the fastest growth in cash flow to produce returns of 9.2 percent so far this year.

Janus Fund was among the biggest investors in technology stocks in the late 1990s and grew to $50 billion in assets before the shares crashed in 2000 and investors pulled money from the Denver-based money manager. This year, Corkins, 40, is beating Fidelity Contrafund's Will Danoff, who has returned 6.3 percent, and the 4.3 percent gain at Value Trust, the Legg Mason fund run by Bill Miller.

"This fund has rocked since Corkins took over," said Karen Dolan, an analyst at research firm Morningstar Inc., of Chicago. "It's more even-keeled."

The fund has three out of a possible five stars from Morningstar. It has a Sharpe ratio of 0.69, compared with 0.60 for other large-company growth funds. A higher Sharpe ratio means better risk-adjusted returns.

The fund, started by Janus founder Thomas Bailey nearly four decades ago, exceeded the returns of 92 percent of the 482 competitors that buy growth stocks, those with above-average sales or profit gains, according to data tracked by Morningstar. The Russell 1000 Growth Index, the fund's benchmark, advanced 6.9 percent this year.

American Funds' $166 billion Growth Fund of America, the biggest in the United States, climbed 6.7 percent, lagging behind 56 percent of its competitors. Vanguard Group's $53 billion Vanguard Windsor II gained 9.1 percent. American Funds is based in Los Angeles, and Vanguard is in Valley Forge.

Miller ended his 15-year record of beating the Standard & Poor's 500 index in 2006, when his $21 billion Baltimore-based Value Trust was hurt by picks such as Sprint Nextel Corp. and UnitedHealth Group Inc. Danoff's $71 billion Contrafund in Boston has been hobbled by Genentech Inc., which declined 3.6 percent this year. Google Inc., the fund's top holding, dropped 1 percent.

Janus chief executive officer Gary Black named Corkins to replace Blaine Rollins, who had trailed the Russell index for three of the five years he managed the fund. Assets in the Janus Fund rose $440 million in the last year.

Corkins, who has a master's degree in business from Columbia University in New York, joined Janus in 1995. He managed the top-performing Janus Mercury Fund and the Janus Growth and Income Fund before assuming his current role.

"There were a lot of growth stocks that stumbled in the late 1990s," Corkins said. "A trap that many managers fell into was that they overestimated growth."

Corkins relies on the firm's 34-member research team to find companies increasing free-cash flow, an indicator of how much a company can invest in growth, at a rate of at least 10 percent a year.

The analysts led Corkins to Precision Castparts Corp., a supplier to jet-engine-makers, and power producer NRG Energy Inc. Shares of Precision Castparts, based in Portland, Ore., jumped 44 percent this year as earnings doubled in the first quarter.

NRG, of Princeton, N.J., jumped 50 percent as electricity prices rose in Texas and the Northeast. The company will start paying dividends next year.

Corkins reduced the number of companies in the fund to about 90 from 135. He sold Juniper Networks Inc. and Boston Scientific Corp., and added JPMorgan Chase & Co., Boeing Co. and TXU Corp., Texas's largest power producer.

Boston Scientific, based in Natick, Mass., dropped 24 percent in the last year as it struggled with the acquisition of Guidant Corp. The sale of Juniper, based in Sunnyvale, Calif., was mistimed. The shares gained 39 percent in the last 12 months.

"The idea was to shrink the number of names," Corkins said, "and invest with conviction."