Samaranch, born into a rich family, had been the chef de mission of the Spanish team at a number of Olympic events, before he was appointed as the government secretary for sports by dictator Franco in 1966, also becoming the president of the Spanish National Olympic Committee and a member of the IOC. He was vice-president of the IOC from 1974 and 1978, and he was appointed as the Spanish ambassador to the Soviet Union and Mongolia from 1977 to 1980.
After the 1980 Summer Olympics, IOC president Lord Michael Killanin resigned and Samaranch was elected as his successor. During his reign, Samaranch managed to make the Olympic Movement financially healthy, with big television deals and sponsorships. Although the 1984 Summer Olympics were still boycotted by the East Block, the number of nations with a membership of the IOC and participating increased at every Games during Samaranch's presidency. Samaranch also wanted the best athletes to compete in the Olympics, which lead to the gradual acceptance of professional athletes.
Samaranch was a controversial figure as the head of the IOC, receiving sustained criticism from a number of former athletes, politicians, and most notably British journalist Andrew Jennings in a series of books and television documentaries. Samaranch was a senior bureaucrat and (arguably) politician in a fascist regime, and many people found such a background repugnant. According to critics, Samaranch was autocratic and intolerant of dissenting voices both within and outside the organisation, with a culture of secrecy surrounding its decisions. A number of incidents of outright corruption of IOC members occurred under Samaranch's reign, which critics claim was indicative of a widespread culture of favours extorted from bidding cities by IOC members. Samaranch did, in his last years in the organisation, take steps to curb some of these excesses, but it is argued that Samaranch must have been aware of the culture for much of his reign and only acted after media pressure.
One achievement of Samaranch has undoubtedly been the financial rescue of the IOC, which was in financial crisis in the 1970s, and the games were such a burden on host cities it appeared that nowhere would be found for future games. Under Samaranch, the IOC revamped its sponsorship arrangements (choosing to go with global sponsors rather than allowing each national federation to take local ones), and new broadcasting deals brought in many millions of dollars. What the IOC does with its new-found millions is, however, the subject of speculation and criticism.