The configuration of E Rosettes with sheep red blood cells and the expression of the epitope detected for the monoclonal antibody anti-CD2 was detected in mononuclear cells from 9 Cebus apella monkeys. Nine human controls were employed, and also the results demostrated the existence of inhibition in the formation of rosettes when anti-CD2 antiboides were used to a maximumdilution of 1/1000