The wide spectrum of clinical manifestations and high relapse rate represent a therapeutic challenge in systemic lupus erythematosus (SLE). Observational studies suggested efficacy of rituximab (RTX), a B-cell-targeting antibody, to control the activity of SLE. Two randomized trials controlled by placebo did not prove the superiority of RTX when used in addition to conventional treatment in nonrenal (EXPLORER) and renal (LUNAR) lupus. A systematic review of studies exploring the efficacy of RTX in SLE patients was conducted. The pooled percentages of response were assessed. Thirty studies with 1243 patients were analyzed. In studies using the British Isles Lupus Assessment Group (BILAG), the complete response (CR) rate was 46.7% (95% CI 36.8%-56.8%) and the partial response (PR) was 37.9% (95% CI 30.6%-45.8%). With the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), the CR was 56.6% (95% CI 32.4%-78.1%) and the PR was 30.9% (95% CI 8.9%-46%). In renal lupus the CR was 36.1% (95% CI 25.2%-48.6%); PR was 37.4% (95% CI 28.5%-47.3%). In EXPLORER, CR was 12.4% and PR was 17.2%; in LUNAR CR was 26.4% and PR was 30.6%, in both cases not different from controls. Assessment and standardization of SLE response to treatment remain a challenge. The discrepancy in the perceived efficacy of RTX between controlled and observational studies reflects the heterogeneity of lupus and stringency in criteria of response. Further randomized trials focusing on selected SLE manifestations and using composite response indices are warranted.