The McKendrick–von Foerster equation is a linear first-order partial differential equation encountered in several areas of mathematical biology – for example, demography and cell proliferation modeling; it is applied when age structure is an important feature in the mathematical model. It was first presented by Anderson Gray McKendrick in 1926 as a deterministic limit of lattice models applied to epidemiology, and subsequently independently in 1959 by biophysics professor Heinz von Foerster for describing cell cycles.