Clayton Oscar Person, CM FRSC (May 16, 1922 – September 1, 1990) was recognized internationally as an authority on the genetics of host-parasite relations.[1] He was born and raised in Aylesbury, Saskatchewan, Canada and died in Vancouver, British Columbia, Canada. His writings have made a major contribution to the development of a rigorous theoretical basis for our understanding of how the genetic structure of parasitic populations interacts with that of their host populations. This was known as the gene-for-gene relationship. His theoretical methods have been applied widely in the practical management of parasitic diseases in agriculture and forestry.