The increasing prevalence of coagulase-negative Staphylococcus (CNS) in systemic infections is associated with risk factors such as immunocompromised state due to cancer, transplant therapy, AIDS, or the increasing use of intravascular catheter or prosthetics devises. For this reason, a coagulase-negative test from a clinical isolate of staphylococci could not be a guarantee of non-virulent, being necessary the performance of another screening test. The presence of Fc receptor for human immunoglobulins at the surface of Staphylococcus constitutes an important virulence factor. The presence of these receptors can be shown by haemagglutination test using an appropriate combination of antibodies and antigens, such as anti-A and Group A red cells. Bacteria sensitized with those antibodies are incubated with group A red cells to measuring their haemaggutination activity. Using this test, 100 strains of Staphylococcus, isolated from clinical samples and from healthy persons were evaluated. The presence of Fc receptors showed a statistical difference with the origin of the strain, the majority (91%) of strains from clinical samples showed those receptors. Twenty five (45%) of the clinical isolates were CNS and 21 (84%) of them showed Fc receptors. These data suggest that the presence of Fc receptor could be a additional factor to judge the possible virulence of coagulase-negative Staphylococcus.