The 2008 TIME 100

In science you learn that the simplest answer is often the best. That's a principle sometimes lost in a world of high-tech medicine—but not on Dr. Peter Pronovost. A critical-care researcher at Johns Hopkins University, Pronovost may have saved more lives than any laboratory scientist in the past decade by relying on a wonderfully simple tool: a checklist.

In the U.S., hospital-acquired infections affect 1 in 10 patients, killing 90,000 of them and costing as much as $11 billion each year. Pronovost, 43, began investigating this alarming trend at Johns Hopkins' hospital in 2001 and concluded that arming physicians with a chart reminding them of each step in routine procedures drastically reduces the medical errors that lead to such infections. After he published his results in several prominent journals, the medical community started listening. Michigan hospitals began implementing Pronovost's checklists in ICUs in 2003. Within three months, hospital-acquired infections at typical ICUs in the state dropped from 2.7 per 1,000 patients to zero. More than 1,500 lives were saved in the first 18 months.

Numbers like this get noticed. California and Spain top a long list of places that soon hope to replicate Michigan's results. Pronovost says the checklist protocol could be rolled out nationwide within two years for less than $3 million. With health-care costs mounting, it's nice to know that one solution requires simply returning to basics.