Grandmaster Kaidanov was born in Berdychiv, Ukrainian SSR, USSR. In 1960, he moved to Kaliningrad, Russian. He learned chess from his father when he was 6 years of age. Kaidanov was a member of US national team in 6 World Chess Olympiads and 3 World Team Championships, winning team Gold (Lucerne, Switzerland 1993), Silver (Lucerne,1997 and Elista, Russia, 1998) and Bronze (Erevan, Armenia 1996). He also won an individual Gold medal in Lucerne 1997 and individual Silver medal in Calvia, Spain in 2004.
Gregory won more than 30 international chess tournaments, including every major American open (World Open, US Open, National Open, Chicago Open, etc) and the first edition of very prestigious Aeroflot Open in Moscow in 2002. He was inducted into the United States Chess Hall of Fame in 2013. Kaidanov has resided in Lexington, Kentucky since 1991, where he coaches the chess team at Sayre School.