The lognormal distribution has been fitted successfully to empirical reaction times (RTs), but mechanisms that might generate lognormally distributed RTs are unknown. Thus, the lognormal has the status of an ad hoc distribution in RT research. The authors describe mechanisms that could generate the lognormal distribution and show how specific RT models can be constructed within the framework of general mathematical properties of the lognormal. It is demonstrated that various conceptually different mechanisms could produce lognormally distributed RTs.