For 50 years, engineers have been searching for reliable and convenient accelerated strength testing methods that would enable them to judge the compressive strength of concrete much sooner then by the traditional 28 day test. As part of this search concrete research workers in Canada have played a leading role in the development of standard procedures. Accelerated methods of the Canadian Standards Association and the American Society for Testing and Materials have now been standardized for use in North America. A study of the pros and cons of each led to the selection of the autogenous curing method as an integral part of the concrete quality assurance program to be used during construction of the CN Tower. In planning the CN Tower project the assessment was made that accelerated strength testing has finally come of age and could advantageously supplant the 28 day test of reassuring the quality and safety of concrete construction on such a major project. On the face of it, the Autogenous Curing Method appears to have several disadvantages: the accelerated strength is not determined until the second day; cements with significantly different rates of generating heat of hydration can affect the results; abnormally low or high concrete temperatures affect the starting temperature and hence the temperature regime generated during the curing period; and the initial cost of the curing containers is high. Practical experience, however, has shown that these disadvantages are not real. The choice ultimately was made based on convenience.