Although the original version of ASTM STP 169, published in 1956, had a chapter written by Scripture entitled “Setting Time,” there was no ASTM standard covering the subject [1]. A method was, however, proposed in 1957 for determining the setting time of concrete under ASTM C 403-57T that was reviewed and discussed by Kelly in ASTM STP 169A in 1966 [2]. In 1978, Sprouse and Peppler continued and updated the work of Kelly in ASTM STP 169B [3]. This chapter is an attempt to merge the historical facts and background information provided by the earlier authors with today's thinking on the subject of time of setting.