A modified protocol for the RAPIDEC Staph system (bioMérieux, Marcy-l'Etoile, France) for direct identification of Staphylococcus aureus in blood cultures was evaluated in a multicenter study. A total of 129 blood cultures (BACTEC 9000 Blood Culture System; Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) containing gram-positive cocci in clusters were analyzed by conventional methods and by RAPIDEC Staph in accordance with the manufacturer's protocol and in accordance with a modified protocol. The sensitivity, specificity, and positive and negative predictive values obtained with the manufacturer's protocol were 90.5, 97.7, 95. 0, and 95.5%, respectively, and those obtained with the modified protocol were 100, 96.6, 93.3, and 100%, respectively. The modified protocol for the RAPIDEC Staph is easier to perform than the manufacturer's protocol and is very reliable.