Background and aim: Rituximab (RTX) therapy has shown promising results in Graves´ disease (GD), with or without ophthalmopathy. We examined the occurrence of adverse events in GD patients treated with RTX. Subjects and methods: Ten patients received RTX and methimazole, while ten patients received methimazole only. Adverse events were recorded, and the presence of circulating immune complexes (CICs) was measured as IgG, IgM and complement component 3 (C3) depositing on normal monocytes following incubation with patient plasma. Results: Five patients had benign infusion-related adverse events at first infusion. Two patients developed a serum sickness-like reaction 11 days after the first RTX-infusion. One of these patients developed diarrhoea, raised orosomucoid levels, low-grade inflammation in colonoscopic biopsies, and iridocyclitis a year later. At day 14, the most pronounced immunoglobulin/C3-adherence to the test monocytes, indicative of CICs, was observed in the presence of plasma from these two patients (p=0.003 to p=0.01 vs. asymptomatic patients). A third patient had recurrent fever and symmetric polyarthritis from day 38, and colonoscopy-verified ulcerative colitis at day 68. This patient had the third highest increase in immunoglobulin deposition on monocytes by day 14. The arthralgias persisted in two of the patients, despite glucocorticoid rescue therapy. Conclusions: We report articular adverse events in three and gastrointestinal symptoms in two out of ten GD patients who received RTX without concurrent immunosupression. The joint symptoms were related to CIC formation.