There are several reports of myeloperoxidase (MPO) playing an important role in acute coronary syndromes (ACS). Interleukin-17 (IL-17) is a pro-inflammatory cytokine produced by activated CD4 T cells that has a chemotactic and activating effect on neutrophils. It has also been shown that IL-17 recruits neutrophils via the release of C-X-C chemokines. The roles of MPO and IL-17 in ACS, however, have not been established. This study measured plasma MPO and IL-17 levels in 10 patients with ACS, 11 age- and sex-matched patients with stable angina and 12 healthy control subjects. Plasma MPO and IL-17 levels were significantly elevated in ACS patients compared with the patients with stable angina and the healthy control subjects. In addition, plasma MPO levels correlated with plasma IL-17 levels in all study participants. It is concluded that MPO and IL-17 are powerful indicators of acute coronary inflammation, however the data set was very small, so larger prospective studies are required.