University of California, Berkeley retained its spot as the nation's top-ranked public university in U.S. News & World Report's annual college ranking, although it shares top billing with the University of Virginia, which ranked second in the last survey.

The magazine's ``America's Best Colleges'' rankings are based on a formula that includes graduation and retention rates, faculty resources, peer review and other factors to determine the standings.

Universities are ranked in a variety of categories.

UC Berkeley and Virginia tied for No. 1 on the listing of the top 50 public universities. On the listing that includes both public and private institutions, the campuses tied at 21st place.

Marie Felde, UC Berkeley's director of media relations, said the campus has been at the top of the public ranking for at least the past decade.

``As in the past, Berkeley has ranked as the No. 1 public university in most of the surveys,'' she said.

For the fourth consecutive year, Princeton University was ranked as the nation's top college, a rating it shared this year with Harvard University, which was second last year.

Yale University ranks third and the Massachusetts Institute of Technology is fourth.

Stanford University tied for fifth with three other colleges - the California Institute of Technology, Duke University and the University of Pennsylvania.

``We've ranked anywhere from No. 1 to No. 6 in recent years,'' said Stanford University spokeswoman Elaine Ray, who said the campus focuses its efforts on undergraduate education. ``We don't lament when we are lower and we don't celebrate when we're higher, we just try to focus on undergraduate education.''

For the first time, U.S. News ranked universities from 1 to 150. Third and fourth-tier schools - those below the 150 mark - are unranked. Last year, the magazine published a top 50 listing, and left second, third and fourth-tier schools unranked.

UC campuses throughout the state continue to earn high rankings on the list of public universities, with eight campuses appearing in the top 50. Six campuses are listed among the top 12.

``UC dominates the public university list,'' said UC spokesman Hanan Eisenman. ``No other state even comes close to that.''

The rankings will be published in Monday's edition of the magazine, and the rankings will be available today on its Web site, www.usnews.com

The rankings are both popular and controversial. Critics have long contended that parents and high school students rely too heavily on the rankings in choosing schools, and that colleges gear some of their efforts - such as admissions - toward getting high rankings.

``We don't like the notion that some colleges are acting in response to the rankings,'' said Brian Kelly, managing editor of U.S. News. ``We think that's a shame.''

Claire Van Ummersen, vice president of the Office of Women in Higher Education for the American Council on Education, said officials have become more accepting of the rankings since they debuted 20 years ago.

``They've been around for a long while and I think people have become more acquainted with them,'' she said. ``While not every institution is happy with them, you do have some that think they're great. ... To some extent, that's determined by where they are in the ranking.''

Officials cautioned the rankings are only one factor prospective students should consider when selecting a college.

``It's a very individual decision,'' said Stanford's Ray. ``One college does not fit all and we hope students will look at the college that best suits them, rather than looking at the rankings.''

In other rankings, Mills College in Oakland tied for 66th among the nation's best liberal arts colleges and University of San Francisco tied for 117th among on the list of the nation's best universities. Among schools that grant master's degrees, Santa Clara University ranked second in the western region, while Sonoma State University tied for 30th.