David Armstrong has had a long and distinguished scientific career in Reproductive Biology. He completed an undergraduate career majoring in animal husbandry at the Ontario Agricultural College in Guelph, Canada, followed by a PhD under the mentorship of Bill Hansel. David moved to the US and completed his postdoctoral studies at Brookhaven National Laboratory and Harvard University after which he joined the Harvard School of Dental Medicine as Assistant Professor of Anatomy. In 1968, he returned to Canada as Professor of Physiology and Obstetrics and Gynaecology at the University of Western Onatario where he founded the Medical Research Council Group and served as its first director from 1979 to 1989. David Armstrong has made numerous significant contributions to the field of Reproductive Biology. With Bill Hansel, he discovered the luteolytic actions of oxytocin on the ovary in cows. This was the first demonstration that a pharmacological agent could terminate corpus luteum function and this also provided one of the earliest means of regulating the oestrous cycle in cattle. In addition, David’s research involving gonadotropins in glucose and cholesterol metabolism provided the first evidence of the role of LH in regulating the biosynthesis of ovarian steroids. He was the first to demonstrate the role of LH in the regulation of progesterone secretion by the corpus luteum in rats and rabbits and thereby establishing the similarity of mechanisms among mammalian species. Perhaps one of David’s most internationally recognised finding stems from his role, together with his collaborators, in providing definitive proof of the “two cell, two gonadotrophin” theory of ovarian oestrogen biosynthesis and regulation. This followed on from their discovery of the biochemical site of action of FSH in stimulating oestrogen production in granulosa cells, and of LH in stimulating androgen production in theca cells. In the early 1990s, David began several collaborations in Australia as visiting Professor, Obstetrics and Gynaecology, at The University of Adelaide and in more recent years as an Emeritus Professor in the Robinson Research Institute at The University of Adelaide. During David’s research career, he has published more than 400 publications, been awarded many research grants and prestigious awards including a NIH Research Career Development Award, election to Fellowship of Royal Society of Canada, honorary D.Sc. degree from the University of Guelph and Hartman Award from Society for the Study of Reproduction (SSR) amongst many others. He has also mentored a large number of graduate students, postdoctoral and clinical fellows (more than 80 in total). In 2015, David returned to Ontario, Canada in his retirement and is still in touch with the scientific community that he helped to establish over his long and very distinguished career.