Men are dirtier than women. So scientists confirmed by spying in public restrooms, watching as one-quarter of men left without washing their hands.

The worst offenders were at an Atlanta Braves game.

In contrast, 90 percent of the women did wash up.

Wednesday's results mark the American Society of Microbiology's latest look at how many people take what is considered the single easiest step to staying healthy: spending 20 seconds rubbing with soap under the faucet.

It also explains why these infection experts tend to use paper towels to open bathroom doors. There is no telling what germs the person before you left on the knob.

"It's a gamble," said microbiologist Judy Daly of Primary Children's Medical Center in Salt Lake City, the society's secretary.

Back in 1996, the society first studied how often people follow mom's advice to always wash up after using the toilet. Researchers lingered in public restrooms, putting on makeup or combing their hair, while surreptitiously counting. They concluded about one-third of people did not wash.

The group sponsored an education campaign about how hand-washing can stop the spread of flu, diarrhea and other infectious diseases. Every few years, researchers repeat the spying.

This time, 83 percent of people washed, reported Harris Interactive, a research company that last month monitored more than 6,300 public restroom users for the society.

That is a little better overall. But take a closer look:

_The worst hygiene was at Atlanta's Turner Field baseball stadium, where 37 percent of men left the bathroom without washing, and 16 percent of the women did.