Background The contribution of regulatory T-cells (Tregs) to systemic lupus erythematosus (SLE) pathogenesis remains a matter of debate. The objective of this study was to quantify the association between peripheral blood Tregs and disease status in SLE patients. Method EMBASE and PubMed databases were searched using 'systemic lupus erythematosus' and 'regulatory T-cells' as relevant key terms. A meta-analysis of studies that examined the proportion of Tregs among peripheral blood mononuclear cells (PBMCs) and CD4(+)T-cells was performed using Stata software. Subgroup analysis was performed based on ethnic groups and Treg definition markers. Results The Treg/PBMC and Treg/CD4(+)T-cell ratios were significantly lower in SLE patients than in healthy controls (HCs), whereas patients with active and inactive SLE showed no difference in these indicators. A subgroup analysis indicated that Asian SLE patients had a substantially lower proportion of Tregs/PBMCs than HCs, but this difference was not seen for white and Latin American SLE patients. Patients defined by CD4(+)CD25(+)Foxp3(+), CD4(+)CD25(+) and CD4(+)Foxp3(+) had a much lower Treg/PBMC ratio compared with HCs. Ethnic groups and choice of Treg definition markers had no influence on the proportion of Tregs/CD4(+)T-cells. Conclusion The proportion of Tregs among both PBMCs and CD4(+)T-cells was significantly decreased in SLE patients. Ethnic group and Treg definition markers may influence the proportion of Tregs among PBMCs. Further study of the correlation between SLE disease activity and the proportion of Tregs in peripheral blood is needed to determine the physiological role of this association.