Injectivity decline due to particles in the injection water takes place to some degree in most injection wells. To understand and predict this decline requires knowledge of the rate of particle deposition for the water/formation system considered. The rate constant for particle deposition is commonly referred to as the filtration coefficient. The filtration coefficient is a dynamic quantity and changes with the number of previously deposited particles. Many investigators have carried out extensive theoretical and experimental work aimed at determining the filtration coefficient under varying conditions. This paper presents a review of past work and its application to injection wells. Tables presenting experimental values for the filtration coefficient as well as theoretical and empirical correlations are reproduced and evaluated. Finally, a new method of determining the development of the filtration coefficient with time, utilizing a concept of critical porosity, is outlined. In particular, this method includes a correlation for the transition time, i.e. the time when an external filter cake starts building on the wellbore.