Followers of the huge Operacion Puerto blood doping scandal will remember the affair - Spanish doctor Eufemiano Fuentes offered a blood doping service to professional sportsmen (and presumably sportswomen). His services are most talked about in the context of professional cycling, but in fact his clients are reported to have included professional sportsmen from other sports.
The saga began with police raids in 2006, when Spain's Guardia Civil collected coded blood bags during its raid on the offices of Doctor Eufemiano Fuentes. (There is excellent coverage over at cyclingnews.com going back several years.) Fuentes' scheme was to withdraw blood from the cyclists, and store it for retransfusion, a process known as blood doping. This is a formerly legal technique (I believe it was used in the past by the US Olympic track cycling team( but it has been prohibited for many years now. It's still clearly in use - witness the sorry tales of (for example) Vinokourov and Hamilton in recent years.