The laboratory isolation of methicillin-resistant Staphylococcus aureus (MRSA) is now commonplace. Part of the screening procedure to detect MRSA rapidly is a reliable particle agglutination test for the presence of S. aureus. Forty clinical isolates of MRSA and 12 of coagulase-negative staphylococci were grown on the three culture media most likely to be used for the isolation of MRSA. Seven particle agglutination kits were evaluated for reliability. Their accuracy and speed of agglutination varied, with four kits, Staphaurex Plus, Pastorex Staph-plus, Slidex and Staphylase, giving better results with the isolates investigated.