Ebert and Panchal introduced the “threshold fouling” approach for describing the initial rate of crude oil chemical reaction fouling at the meeting in this series of conferences held in San Luis Obispo, CA, in 1995. This paper summarizes reviews of developments in the threshold modeling approach over the last 10 years, following the review by Wilson et al. at the 2005 meeting. Three areas are considered: (i) The development of quantitative models, which has seen little activity but a switch toward using the threshold models to describe fouling dynamics. One of the reasons for the stagnation in development is the need to incorporate chemical understanding. (ii) The types and range of data sets that have been processed with these models, and an evaluation of the parameters. (iii) Applications where the models are used to predict fouling, or the likelihood of fouling. This is the area that has seen greatest activity, linked to the use of threshold models to describe fouling dynamics. Topics for future research and development are discussed.