We investigated whether peripheral monocytes from periodontitis patients (52.6 ± 5.1 years old; 2 females and 3 males) present differential S100A12 expression and secretion when compared with monocytes from periodontally healthy participants (42.4 ± 15.9 years old; 3 females and 2 males), and whether this difference was related to a particular subset. This evidence concerns the gene S100A12 and periodontitis.