Throughout the case, Fuentes has said that he never endangered the health of his clients and that the blood transfusions he gave them helped them with anemia and did not provide any boost in performance.

Several of the best cyclists in recent history, including the Olympic gold medalist Tyler Hamilton, the former Tour de France winner Jan Ullrich and the Giro d’Italia winner Ivan Basso, have been implicated in the Fuentes doping ring. The names of any noncyclists who were clients of Fuentes were never revealed, but during the trial there were hints.

On one day of the trial, Fuentes told reporters that the team Real Madrid owed him money, but would not say whether that debt stemmed from treating Madrid players with performance-enhancing drugs or transfusions. He later said that he never gave Madrid players any drugs. The club said the debt was for Fuentes testifying on its behalf in another trial. Prosecutors also questioned Fuentes about the letters “RSoc” on some paperwork it had confiscated from him, suggesting that those letters possibly stood for the soccer team Real Sociedad, the Basque soccer club. Fuentes said he did not know what those letters meant, and he later told reporters that those letters sounded like the name of a good wine.

Only one of Fuentes’s colleagues, Ignacio Labarta, a former trainer for the cycling team Kelme, was convicted with him Tuesday. Labarta was handed a suspended four-month sentence for his involvement in doping athletes. Three others charged in the case — Yolanda Fuentes, who is Fuentes’s sister; the former Liberty Seguros cycling team manager Manolo Saiz; and the former Kelme cycling team director Vicente Belda — were acquitted.

Testimony in the Operation Puerto case lasted about two months, ending in early April. Hamilton, who also was a key witness in the United States Anti-Doping Agency’s doping case against Lance Armstrong that led to Armstrong’s receiving a lifetime ban from Olympic sports, testified against Fuentes in February.

Hamilton claimed that he began to see Fuentes in 2002 when he raced for the team CSC. He said that Bjarne Riis, the team director of CSC, had introduced him to the doctor, and that the doctor had given him the endurance-boosting drug EPO, testosterone and growth hormone. He also testified that Fuentes had helped him with blood transfusions about 15 times, including once during the 2004 Tour. After receiving that transfusion in 2004, Hamilton said he felt ill and his urine had turned black. He said one of Fuentes’s helpers, Alberto León, at least once reinfused him with blood, although León had no medical training. León committed suicide in 2011.