NEW YORK ( TheStreet Ratings) -- Ratings ranked 14,478 open-end stock mutual funds offered by 461 different fund families on the basis of risk-adjusted return for our Winter 2011-12 Guide to Stock Mutual Funds. The top 30% of funds with grades of B+ or better are considered to be 'Buys', the middle 40% 'Holds' have grade in the C range, and the lower 30% 'Sells' have grades of D+ or worse.

The fund families placing a higher percentage of their funds in the top 30% of our year-end rankings than their peers are considered to be 'Ultra' fund families. Peer groups include fund families with 100 or more rated funds, 40 to 99 rated funds, 10 to 39 rated funds, and 1 to 9 rated funds.

T. Rowe Price Funds, a unit of T. Rowe Price Group ( TROW - Get Report) placed 79 of its 122 rated funds in the top 30% of TheStreet Ratings ranking of open-end stock mutual funds. So, T. Rowe Price wins top 'Ultra' fund family honors among families with 100 or more rated funds.

See the list of the top rated T. Rowe Price funds in our Ratings Research Center. The list includes A+ rated funds such as T Rowe Price Cap Appreciation ( PRWCX - Get Report) and T Rowe Price Science and Tech ( PRSCX - Get Report).

The runner-up 'Ultra' fund family in the 100 plus group is Vanguard Funds. Vanguard finished the year with 102 of its 215 rated funds in the 'buy' range of B+ or better.

See the list of the top rated Vanguard funds in our Ratings Research Center. The list includes A+ rated funds such as Vanguard Consumer Staples Index Adm ( VCSAX - Get Report) and Vanguard Information Technology Index Adm ( VITAX - Get Report).

Topping the 'Ultra' fund family list of large groups with 40 to 99 rated funds are three families that all placed more than half of their rated funds in the top 30% of our rankings. Delaware Investments outperformed on 56.4% of its 94 rated funds. Alger Funds followed with 52.9% of its 51 rated funds in the 'buy' range. And, Royce Funds rounds out the best three at 52.8% of its 72 rated funds on top.

While none of these three families have their own top rated funds page, you can still view a find a list of their funds in our mutual fund screener. For example, click on the "FUNDS" tab. Select "Delaware Investments" from the "Fund Family" drop-down menu. Then drag the lower bound "Overall Rating" slider to the left so that only funds rated in the green range from A+ down to B- are shown including A+ rated Delaware Dividend Income B ( DDDBX).

The smaller 'Ultra' fund family list of groups with 10 to 39 rated funds is led by Wasatch Funds with 12 of its 13 rated funds in the top 30% of our rankings. The Wasatch Heritage Growth Fund ( WAHGX) and Wasatch World Innovators Fund ( WAGTX - Get Report) both earned our best possible 'Excellent' rating of A+ for the period ending Dec 31, 2011.

The Brown Advisory Funds group placed 72.7% of their 11 rated funds in the 'buy' range including A+ rated Brown Advisory Flexible Value Adv ( BAFVX) . The Sentinel Group with 60% top rated funds earns an honorable mention with funds such as Sentinel Mid Cap I ( SIMGX).

Of the fund families with less than 10 rated funds, the 'Ultra' fund family winner is Nicholas Funds with all eight of their funds ranked at 'buy' including the A+ rated Nicholas High Income I ( NCINX - Get Report).

Luther King Capital Management was in second place with all seven of their rated funds on top including the A- rated LKCM Aquinas Small-Cap Fund ( AQBLX).

Third place winner, Weitz Series, finished the year with all five of their rated funds in the top ranks. The Weitz Balanced Fund ( WBALX - Get Report) is rated at A+.

Research Methodology Ratings condenses the available fund performance and risk data into a single composite opinion of each fund's risk-adjusted performance. This allows the unbiased identification of those funds that have historically done well and those that have underperformed the market.

While there is no guarantee of future performance, these Investment Ratings provide a solid framework for making informed, timely investment decisions. In order to qualify for a rating, an open-end fund must either have three years of risk and return data or be an additional share class of an existing fund with at least three years of performance statistics. Some related fund families of the same parent company have been grouped together.

Funds rated A or B are considered "Buy" rated based on a track record of higher than average risk-adjusted performance. Funds at the C level are rated as "Hold," while underperformers at the D and E levels our model ranks as "Sell."

-- Reported by Kevin Baker in Jupiter, Fla.

Kevin Baker became the senior financial analyst for TheStreet Ratings upon the August 2006 acquisition of Weiss Ratings by, covering equity and mutual fund ratings. He joined the Weiss Group in 1997 as a banking and brokerage analyst. In 1999, he created the Weiss Group's first ratings to gauge the level of risk in U.S. equities. Baker received a B.S. degree in management from Rensselaer Polytechnic Institute and an M.B.A. with a finance specialization from Nova Southeastern University.