One-third of men didn't wash after using the bathroom, compared with 12 percent of women, said the researchers who spy on people in public restrooms. They reported their findings Monday at a meeting of infectious disease scientists.

Two years ago, only one-quarter of men didn't wash, compared with 10 percent of women.

The latest study was based on observations last month of more than 6,000 people in four big cities.

Frequent hand washing is the single best thing people can do to avoid getting sick, doctors say. A recent Harris Interactive survey found 92 percent of Americans said they always wash up after using the bathroom.

The dirty details:

* ATLANTA'S TURNER FIELD baseball stadium again was the worst. Fifty-seven percent of guys there washed up, compared to 95 percent of women.

* NEW YORK was Second City to Chicago in cleanliness. At the Windy City's Shedd Aquarium and Museum of Science and Industry, 81 percent of men and women combined washed, compared to 79 percent at Penn and Grand Central train stations.

* AT SAN FRANCISCO's Ferry Terminal Farmers Market, 62.5 percent of men lathered up. Women were 84 percent.