Robert Keith Guild qualified as a Bachelor of Medicine (MB) and Master of Surgery (CM) at the University of Aberdeen, Scotland, in 1876 and was licensed to practice in the Cape Colony in February the next year. He was a member of the South African Philosophical Society from about 1883 to about 1887. By 1884 he had settled in Griqualand East, where he became district surgeon. In 1892 he requested a license to practice also as a chemist and druggist, but this does not appear to have been granted. He was living in Kokstad, Griqualand East, in 1893.
In 1886 Dr Guild published a 16-page pamphlet titled Leprosy in King William's Town. Five years later he sent a package to the secretary of the Leprosy Investigation Committee of the National Leprosy Fund in England. He appears to have died in or before 1899, for a case was pending against his widow that year. However, another Robert Keith Guild, perhaps his son, died in the Transvaal in 1941.