Peter Yarrow now sings of colonoscopies

Not everyone has the guts to write an ode to colonoscopy. But legendary singer-songwriter Peter Yarrow, of the 1960s folk trio Peter, Paul and Mary, is no stranger to squeamish issues. If "The Colonoscopy Song" saves just one life, he's certain it will be worth the potential ridicule.

"People are uncomfortable talking about colonoscopies," said Yarrow, 71, who wrote the song after doctors discovered a potentially cancerous polyp during his own procedure. Catch Yarrow singing the song on YouTube.com.

For 50 years, Yarrow has supported social and political causes.

But it wasn't until he waxed poetic about colon exams to raise awareness about colon cancer that he received his own billboard along New York's Long Island Expressway.

Unlike Yarrow's classic children's song "Puff the Magic Dragon," "The Colonoscopy Song" is not something you want to sing to your 5-year-old. Though both address the hardships of growing older, the colonoscopy song is a bit more graphic: It describes the procedure, which involves sticking a camera where the sun doesn't shine.

What you won't find are veiled references to medical marijuana. Though he believes medical marijuana is an important issue, cancer screening is one of his highest priorities - along with justice and freedom - especially after the death of his longtime friend and bandmate Mary Travers.