THE SLIM, PALE BLUE ENVELOPE arrived in the mailbox with a soft and devastating pffft, sending UC applicants into a tizzy. Could they be so hopelessly subpar that the University of California rejected their applications two months early?

But no. The heart attack-inducing letters sent to freshman applicants last month were just part of the University of California's 2-year-old application verification process, spot checks on what has traditionally been an honor system.

Were you really an eight-hour-a-week lifeguard last summer? Do you really play the tuba?

And the biggest question of all: How many applicants lied?

Whether applying online or via low-tech paper, high school seniors are honor-bound as they describe their academic and extracurricular experiences. Grades of accepted applicants are eventually verified with official high school transcripts. Test scores flow in from the College Board.

But your year of varsity bowling? Admissions officers trust that those eager 17-year-olds haven't concocted faux extracurriculars. Or rather, they trust them up to a point.

What began as a fact-checking test of 437 UC San Diego applications in 2001-02 went systemwide last year. UC spokesman Hanan Eisenman says the university double-checked details on 10 percent of applications in 2003, and another 10 percent this year -- some 4,500 applications in the past few weeks.

Eisenman says the "freshman verification" process was done to reassure applicants.

The slim envelope that hit mailboxes in January contained a letter of explanation and a highlighted copy of the student's application. Find the yellow stripe in one of seven areas -- honors, extracurricular activities, community service and so forth. Now, provide backup documentation.

A newspaper review of your debut with the Sydney Opera will do nicely, but the admissions processing center in Concord also will accept a note from your music director -- on letterhead. Built latrines in Mexico? Saved endangered turtles in Costa Rica? Let's see the photos.

"UCLA stated last year that the students were remarkably honest," said Larry Cebull, head counselor at Miramonte High School. "Kids tend to be honest when they are told that their admission will be withdrawn if any fraud is found. We certainly pound that statement in."

Indeed, most students are very honest, Eisenman said. But given the escalating competitiveness of the college admissions process, counselors said some students were concerned that other students might be exaggerating their accomplishments.

A UC Academic Senate document points to that increased competition and "the public's increasing awareness of the importance ... of nonacademic information," before concluding that "the university has a responsibility to do what it can to reassure applicants and the general public that the information on which admission decisions are based is accurate."

So, how many 17- and 18-year-olds lied on their UC applications for 2003?

Zero, Eisenman says.

"We didn't uncover any students who had exaggerated or falsified their applications."