The report comprises a review and analysis of the available literature pertaining to the causes, effects and prevention of secondary (delayed) ettringite in concrete . Over 300 publications have been examined . Case studies of damage in concrete possibly caused by secondary ettringite formation are examined first. Fundamental research on secondary ettringite formation, its chemistry, and deposition mechanisms is then reviewed. Key investigations on the topic are analyzed in detail. Next, the potential importance of (a) method of heat-curing and (b) the chemistry of cement is outlined. In the final chapter, a rapid test for evaluation of potential secondary ettringite susceptibility (the "Duggan" test) is evaluated. The analysis indicates that there appears to be a potential for a secondary ettringite formation problem in North America; it is highly probable that secondary ettringite formation can lead to significant deterioration of heat-treated concrete. However, it is unlikely that secondary ettringite formation is, or will be, the sole mechanism responsible for premature deterioration. The critical factors that determine extent of damage due to secondary ettringite formation are (a) duration of delay period before heating the concrete; (b) severity of the heating and/or cooling regime ; and (c) the SO3/A1203 ratio of the cement. There is no evidence that nonheat-treated concrete is susceptible to this phenomenon. Further research and improvements to the Duggan test may result in the development of a useful standard test method to assess the long-term dimensional stability and durability of concrete.