A probability theory has been developed for the description of cellular uptake and recycling of ligands. The theory is non dependent on the mechanism of uptake, processing and secretion of ligands. The probability of finding a ligand attached to, or residing inside a cell is only related to the concentration of ligand in the medium, the probability of uptake and the probability of secretion, as S(n) = ab(1 - 2 - b n ) +1 α n - 1 β n , where S is the intracellular concentration of ligand, n is the exposure of the cell to ligand, a is the probability of independent binding to a receptor, α relates to the probability of self-dependent uptake, b is the probability of dissociation from a receptor and β relates to the probability of secretion from the cell.The simple game theory can well describe experimental data on cellular uptake of transferrin by cultured hepatoma cell lines and glutamate uptake by primary cultures of glial cells.