Dr Reinhart Straszacker and Dr Hendrik Roelof van Huyssteen (both RSA) played their first game of correspondence chess in 1946. After 112 matches, with both men having won half the games, their record play of over 53 years ended with the death of Straszacker on 13 October 1999.
The two men eventually met in 1969. After their first two games, the pair would have four matches on the go at the same time.
Comments below may relate to previous holders of this record.