"If you don't have a girlfriend or a boyfriend, they say you are crazy, don't they?" 23-year-old Alex Mumale asked the youngsters as they banged drums and blew trumpets.
"Well, we say we are crazy. We are crazy about Jesus, because he is our redeemer and our shield," he said to loud applause from the crowd and from First Lady Janet Museveni.
Many of the group, most of them in their late teens, waved colorful banners carrying messages like "Abstinence is safe and healthy" and "Condoms are completely not effective."
Most had rejected sex before marriage for religious reasons, and to avoid HIV/AIDS and other sexually transmitted diseases.
"I chose abstinence because it is a smart way to protect my life," said third-year science student Diana Nambatya.
Organized by several church and youth groups, including the U.S.-based True Love Waits program, the meeting drew more than 500 committed virgins from across the East African country once seen as the epicenter of the HIV/AIDS epidemic.
An energetic government information campaign helped bring down infection rates to about six percent from more than 30 percent in the early 1990s, and the government says promoting abstinence will be key to reducing the future prevalence of the disease.
"You are all created in the image of God, and God has endowed you with the ability of self-control. We are here to guide you to a safer way of life," Mrs. Museveni told the crowd.
After praying together, the youths released bunches of balloons into the deep blue sky, saying they wanted to send their message of patience to the rest of the country.
Pastor Martin Sempa, a vocal advocate of abstinence, said events like Friday's were crucial because the mainstream media was biased in their presentation of the issue.
"You can sense the cynicism and animosity," he told Reuters. "We are promoting abstinence because Uganda is under attack from an agenda driven by homosexuals and Western experts who are out of touch with how the AIDS epidemic is driven in Africa."
As he spoke, a group of teenage boys walked past carrying a homemade sign saying: "Please open your eyes and ears homos."
Jimmy Bosco, a Ugandan activist for True Love Waits, said premarital sex was forbidden in traditional African cultures.
"Some girls who messed around would even be thrown to wild animals, or their parents fined many goats," he told Reuters.
On stage, Uganda Youth Forum Chairman Sam Ruboga worked the crowd into a frenzy with shouts of "Abstinence, oh-yeah!"
He said they should abstain from sex now, keeping their "valuables" until later, when they would enjoy it more.
"You know what it is like when you eat a young, unripe mango?" he asked. "That's right. It is very, very bitter."