We observed cultured retinal pigment epithelial cells as they responded to the introduction of latex particles. The cells showed phagocytosis of particles 1 h after administration of latex and were filled with particles after 24 h. After 7 days, exocytosis of latex from basal plasma membrane was documented. Observation was repeated using a two-layer culture. 7 days after putting the retinal pigment epithelial layer containing latex particles on another layer without particles, we observed the appearance of latex particles in the lower layer that originally contained no particles. This demonstrated that cultured retinal pigment epithelial cells exocytose latex particles from basal cell membrane.