The Coming of Age of WI-381 1This work was not supported in whole or in part by Grant R01 AG 03478 from the National Institute on Aging, NIH, Bethesda, Md.2 2A version of this paper was presented at the thirty-fourth annual meeting of the Tissue Culture Association, at the Session-in-Depth, “Origin of Cell Lines,” organized and chaired by Dr. Robert E. Stevenson, Orlando, Florida, 13 June 1983. This was an invited paper in which Dr. Stevenson requested an historical perspective on the development of the human diploid cell strains, in particular WI-38 with no technical details, since they can be found in the literature (14, 19). He requested “introspection that may yield some interesting insights into the process of scientific thought and motivation of scientists … because the scientific literature seldom contains such information and future generations of scientists may never know this important and often misunderstood background of thinking and motivation unless you tell it directly. Also, in retrospect, how do you feel now about your approach? And what would you do differently today, given your interim experience and the current state of the art? In sum, this is a license to philosophize and distill your wisdom.”The invitation to present this paper could not have come at a more propitious time. Believe it or not, this year marks the twenty-first birthday of WI-38. The cells have reached their majority. Since they are normal human cells, they actually fulfill all the criteria necessary to obtain a voting registration card. Indeed, they are the first cultured normal human cell population to ever reach voting age. But, alas, they contain no brain cells. However, that never was a requirement for voting rights in this country.