NEW YORK ( TheStreet Ratings) -- TheStreet.com Ratings ranked 14,404 open-end stock mutual funds offered by 465 different fund families on the basis of risk-adjusted return for our Summer 2012 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. The 'Ultra' fund family winner in the 100 plus group is Vanguard Funds. Vanguard finished the quarter with 137 of its 237 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 Stap Index Adm ( VCSAX) and Vanguard Health Care Inv ( VGHCX). T. Rowe Price Funds, a unit of T. Rowe Price Group ( TROW) placed 58 of its 124 rated funds in the top 30% of TheStreet Ratings ranking of open-end stock mutual funds. So, T. Rowe Price is the runner-up 'Ultra' fund family 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 Health Sciences ( PRHSX) and T Rowe Price Equity Index 500 ( PREIX). T. Rowe Price and Vanguard swapped their positions as the top two fund families ranked last quarter as listed in TheStreet Ratings 2012 First Quarter Ultra Fund Families article.