Leonid Ilyichov was the best Soviet freestyle sprinter of the 1960s. During his career, Ilyichov competed at the 1966 and 1970 European Championships and 1968 Olympics, winning one individual and eight relay medals at those championships. His only individual medal came at the 1966 European Championships, where he won silver in the 100 free. At that event he also won 4×200 free relay and medley relay titles, as well as a 4×100 free relay silver. At the 1968 Olympic Games Ilyichov won silver in the 4×100 free relay and bronze in the 4×200 relay and medley relay. He was also fifth in the 100 freestyle at the 1968 Olympics. At the 1970 European Championships Ilyichov won his third European title, in the 4×100 freestyle relay, with a bronze in the medley relay, also placing fourth in the 100 free. Domestically, Ilyichov won 12 Soviet titles: 100 freestyle: 1965-70; 200 freestyle: 1966-69; 4×100 free relay in 1969; and 4×200 free relay in 1965. Ilyichov retired from swimming in 1971 and later worked as a swimming coach in Moscow.
Personal Bests: 100 m freestyle – 53.3 (1967); 200 m freestyle – 1:56.9 (1967).