The withdrawal of oral anticoagulation (OAC) in patients with SLE and secondary aPL syndrome (SAPS) who become seronegative has not been clearly investigated to date. Our aim was to evaluate the prevalence of aPL seroconversion and the prognosis of SLE patients with SAPS who withdrew OAC after aPL negativization.We retrospectively analysed data of all SLE patients (ACR criteria) with SAPS (Sydney criteria) prospectively followed-up in our clinic. aPL seroconversion was defined as negativization of lupus anticoagulant, aCL, and anti-β2glycoprotein-1 antibodies on two or more consecutive measurements, at least 12 weeks apart. OAC discontinuation was defined as the definitive withdrawal of all anticoagulants.Fifty-five out of 513 (10.7%) SLE patients had vascular SAPS. Sixteen patients (29.1%) became aPL seronegative during follow-up. Immunosuppressive therapy predicted aPL negativization (odds ratio 5.211, 95%CI 1.341, 20.243), whereas APS diagnosis prior to that of SLE (odds ratio 0.078, 95%CI 0.008, 0.799) and triple-positive profile (odds ratio 0.264, 95%CI 0.115, 0.609) were negative predictors of aPL negativization. OAC was discontinued in 13/55 patients (23.6%), after a median follow-up of 45 months (range 1-276) from aPL seroconversion. SLE-related modifiable risk factors for thrombosis were observed in 10/13 patients (77%) at the time of the thrombotic event. No thrombotic recurrences were observed during a mean follow-up time of 44 (19) months from OAC discontinuation.Our results suggest that OAC can be safely discontinued in SLE patients who became persistently seronegative for aPL, at least when aPL-related thrombotic events occurred in presence of other thrombotic risk factors.