Synovitis in toxic shock syndrome (TSS) is an unusual finding. A 31‐year‐old man presented with pain and swelling in both knees and was found to have TSS, secondary to a septic bursitis caused by Staphylococcus aureus. Immune complexes were not detected in serum or synovial fluid, and the S aureus was not recovered from the inflamed joints. Antibodies against the TSS toxin‐1 were detected in serum and synovial fluid, but in lower levels than would be seen in a normal control serum. Complement studies implicated alternative pathway activation by a marked diminution in C3 levels compared with C4 levels, and by lower levels of factor B than would be found in other inflammatory joint diseases. The diagnostic dilemma posed by TSS in a man is discussed.