Macrophage activation syndrome (MAS) is a devastating complication of systemic JIA (sJIA), seen in approximately 10-25% of the sJIA patients. A number of criteria have been proposed to differentiate between activation of sJIA and MAS, including HScore and the recently proposed MS-score. This is the first study comparing the performances of MS-score and HScore for the diagnosis of MAS in sJIA patients. Systemic JIA patients followed at Hacettepe University Pediatric Rheumatology Unit were included in the study. Clinical features and laboratory findings at the time when the disease was most active or patients were diagnosed with MAS were recorded retrospectively. HScore and MS-score were calculated and the diagnostic performance for MAS was compared by receiver operating characteristic (ROC) curve analysis. Seventy-one sJIA patients were included (23 MAS, 48 activation). There was no difference in age of onset (median 4.7 vs. 5.0 years) and gender (73.9% vs. 54.2%) between patients who had MAS and sJIA activation. Median MS-score and HScore were higher in the MAS group. ROC curve analysis revealed that the HScore performed slightly better in diagnosing MAS, compared with the MS-score (AUC = 0.965 and 0.901 for HScore and MS-score respectively, P < 0.001). In our cohort, the optimal cut-off for the MS score was >= - 1.64 (sensitivity: 91.3%; specificity: 83.8%) and for the HScore it was >= 162.5 (sensitivity: 91.3%; specificity: 90.2%). HScore performed slightly better than MS-score for the diagnosis of MAS in our cohort.