Objectives: To determine if the use of Hydroxychloroquine (HCQ) is associated with a reduction of the frequency and severity of SLE flares over a 12-month period. Methods: Prospective, observational study of SLE patients (SLICC/ACR, 2012 classification criteria) receiving corticosteroid (CS) treatment with/without cytostatic drugs and not receiving HCQ. The patients were divided into two groups: basic SLE treatment without HCQ– G0 and basic SLE treatment plus HCQ 6,5mg/kg body weight – G1. The frequency and severity of SLE flares were assessed by SELENA/SLEDAI flare index. Results: The variables of G0 and G1 at baseline are shown in the table 1.We have determined that in G0 occurred 36 flares, including 10 cases of severe flares, vs G1, where only 19 flares were unregistered, including one severe flare (p<0,05). The relative risk (RR) for G1 vs G0 of flares is presented in the table 2.Conclusions: The use of Hydroxychloroquine was associated with a decrease of the frequency of SLE flares as assessed by SELENA/SLEDAI flare index (RR for flares at 6 months of HCQ use =0,5, 95%CI=0,25–0,98, RR for flares at 12 months of HCQ use = 0,49, 95%CI=0,25–0,94).