<p>The present work presents a critical review on the ionization degree of the micelles (α), analyzing its derivation from electrostatics, as well as the influence of different factors and their interpretation. We have considered the effect of the hydrocarbon chain length, the aggregation number, the polar group’s size and hydrolysis, the counterions´ charge and cases when non-ionic surfactants or alcohol molecules are included into ionic micelles. The appropriate interpretation of α depends not only on the nature of the system studied but also on the methodology employed for its determination. We have concluded that the most appropriate denomination for this property is <i>degree of counterion release</i>.</p> Graphical Abstract <p></p>