Children affected by attention deficit/hyperactivity disorder are often treated with methylphenidate (MPH). Two years ago, an increase in genomic damage after 3 months of MPH treatment was reported by researchers from Texas, U.S.A., raising concern about potential carcinogenic effects. In a similar investigation conducted in Wuerzburg, Germany, we did not find a comparable elevation of genomic damage. MPH is not genotoxic in standard test systems, but yielded one positive result in a rodent carcinogenicity study at the highest test dose only (60-fold above therapeutic doses). In conclusion, changes in treatment strategies do not seem justified currently. Larger studies are under way and will hopefully eliminate any remaining doubt about potential genotoxic or carcinogenic consequences of MPH treatment.