The ability of cultured bovine trabecular meshwork cells to phagocytose latex microspheres was studied by electron microscopy. In addition, the incorporation of 125I gamma-globulin-coated microspheres by the meshwork cells was monitored. The cultured cells, on the basis of quantitation by scanning electron microscopy, did not show significant preference between biotic particles (gamma-globulin-coated microspheres) and abiotic particles (uncoated microspheres). Surface microvilli appeared to be involved in the initial stages of phagocytosis; indeed a significant negative correlation was demonstrated between the incidence of microvilli and the commitment to phagocytosis of preconfluent cells. Two weeks postconfluent cells were shown to be significantly less phagocytic than preconfluent cells. The importance of these findings in terms of the behaviour of meshwork cells in vivo is discussed.