One hundred and seventy three clinical isolates of mannitol fermenter staphylococci, including 120 S. aureus (38% methicillin resistant) and 53 coagulase negative staphylococci were assayed for direct detection of S. aureus on colonies. Three new rapid slide agglutination tests were compared: Pastorex Staph Plus, Slidex Staph Kit and Staph aureus. Each one detects fibrinogen receptor and protein A. According to the addition of monoclonal antibodies, Pastorex Staph plus is intended to detect capsular antigens 5 and 8, and Slidex Staph kit to detect a surface glycopolysaccharide. Sensitivities of these tests were equal, Pastorex Staph plus 95%, Slidex Staph kit 94.2%, Staph aureus 95.8%. Among meticillin-resistant S. aureus, sensitivities reached 91.3%, 87% and 91.3% respectively. Specificities over coagulase negative staphylococci which gave conclusive results were 92.5%, 90.2% and 90.4% respectively. The validity of these results was checked over 100 staphylococcal primary isolates of medical samples in April 1994. Over 62 S. aureus (29% methicillin-resistant) Pastorex Staph plus and Staph aureus sensitivities were 96.8% and 98.4% respectively and specificities were 94.6% and 91.9% over 37 coagulase negative staphylococci which gave conclusive results. Staph aureus test sensitivity is at least equivalent to second generation tests as well in primary cultures as in subcultures The best specifity is achieved with Pastorex Staph plus, which contains latex particles without red blood cells.