Using cultured A431 cells, a comparative analysis was performed of endocytosis stimulated by the epidermal growth factor (EGF) just following the ligand influence (early endocytosis) and after a 3 hour incubation of A431 cells with EGF (delay endocytosis). It is shown that at the early endocytosis the total amount of 125I-EGF, associated with cells, is decreased less than at the delay endocytosis. The decrease in total amount of cell-associated 125I-EGF was accompanied with the increase in the EGF concentration in the incubation medium. The data obtained suggested a lower rate of internalization for delay endocytosis. The Scatchard analysis of 125I-EGF-binding has shown that both high affinity EGF-receptor and low affinity EGF-receptor undergo the down-regulation. The Percoll gradient fractionation of EGF-loaded cells has shown that at the delay endocytosis 125I-EGF is displaced to the fraction of heavy endosomes and lysosomes slower than at the early endocytosis. It is suggested that a delay of EGF-receptor complexes transition from endosomes to lysosomes may arise during delay endocytosis.