Terentyev was born in a large Karelian family of nine siblings and spoke Finnish. Although he skied since early age, he started training on a proper equipment only when he joined the Soviet Army in 1944. In 1950 he finished second in the 4×10 km relay at the Soviet Championships, and in 1951 placed third in the individual 18 and 30 km races; he won all these three events in 1954 and was included into the national team.
Terentyev was born into a large Karelian family of nine siblings and spoke Finnish. Although he skied from an early age, he began training with proper equipment only when he joined the Soviet Army in 1944. In 1950, he finished second in the 4×10 km relay at the Soviet Championships, and in 1951, he placed third in both the individual 18 and 30 km races; he won all three events in 1954 and was included on the national team.