In the aftermath of the performance-enhancing drugs crisis in cycling following the 1998 Tour de France, Riis acquired the nickname of Mr. 60%, a suggestion that he has used doping. The 60% is an allusion to a high hematocrit (red blood cell) level, an indication of EPO usage. It has been published, but never proven, that Riis had a hematocrit level of 56% during one test in July 1995; well above typical natural levels, as well as his published reading of 41% in the offseason earlier that year. The earliest mention of the nickname can be traced to interviews with riders of Festina in 1998–2000, who apparently suggested that if they had been doped above 50%, then Riis must have been doped to at least 60%, since he was able to win the Tour de France in 1996 ahead of the Festina rider Richard Virenque: in Willy Voet's book Breaking the Chain, he mentions that Festina's team doctor would not allow EPO to be administered if a rider's hematocrit level was near 55%.