In June, Dutch scientists finished the largest study yet to find out whether erythropoietin (EPO), a drug popular among professional cyclists, really enhances athletic performance. The researchers recruited 48 trained amateur cyclists and gave them either EPO or a placebo for 8 weeks. Participants were subjected to seven endurance tests, culminating in a race up the Mont Ventoux in France, one of cycling’s legendary ascents. The researchers are still analyzing results but have already shared one key outcome: Riders on EPO weren’t faster than those on placebo. Other researchers find it hard to believe that EPO would do nothing, based on previous studies and athletes’ stories. But they applaud the team for subjecting EPO to a large randomized controlled trial, the gold standard in medicine.