Rituximab (RTX) is currently used in many diseases, but its efficacy and safety in juvenile systemic lupus erythematosus (SLEj) is still unknown. In this chapter we present four case reports of children treated with RTX: three SLE and one immune thrombocytopenic purpura (ITP). Two of the three SLEj patients had class IV lupus nephritis (LN) and hematologic manifestations (pancytopenia), both reaching complete recovery of blood counts and improvement of LN with RTX treatment. Our third SLE patient had a severe onset with generalized microangiopathic manifestations in association with antiphospholipid antibodies and has been in remission for almost 1 year after RTX. However, our fourth case, a patient with ITP and renal failure, was treated with RTX without either hematologic or renal response.