[2] He is known for his research into the biochemical effects of cancer,[3] contributions to the pharmacology of arsenicals[4][5] and the discovery, with Homer Smith, of mapharsen as the active agent in Paul Ehrlich's Salvarsan.

He obtained a doctorate under the supervision of Ludwig Gattermann at the University of Freiburg, Germany in 1902, with a thesis entitled Beiträge zur Kenntnis des Phenyläthers und seiner Homologen (Contribution to the study of phenylether and its homologues).

In 1906, he was appointed assistant professor to John Jacob Abel, head of the pharmacology department.

[1] In 1913, succeeding Reid Hunt, Voegtlin was promoted to head the pharmacology section of the U.S. Hygienic Laboratory, which in 1937 became the National Institutes of Health.

He held this post until 1940, but remained in the health service until 1943, when he retired, having been appointed Director of the National Cancer Institute in 1938.