Clinical guidelines recommend that adults with hypertension self-monitor their blood pressure (BP). To summarize evidence about the effectiveness of self-measured blood pressure (SMBP) monitoring in adults with hypertension. MEDLINE (inception to 8 February 2013) and Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews (fourth quarter 2012). 52 prospective comparative studies of SMBP monitoring with or without additional support versus usual care or an alternative SMBP monitoring intervention in persons with hypertension. Data on population, interventions, BP, other outcomes, and study method were extracted. Random-effects model meta-analyses were done. For SMBP monitoring alone versus usual care (26 comparisons), moderate-strength evidence supports a lower BP with SMBP monitoring at 6 months (summary net difference, -3.9 mm Hg and -2.4 mm Hg for systolic BP and diastolic BP) but not at 12 months. For SMBP monitoring plus additional support versus usual care (25 comparisons), high-strength evidence supports a lower BP with use of SMBP monitoring, ranging from -3.4 to -8.9 mm Hg for systolic BP and from -1.9 to -4.4 mm Hg for diastolic BP, at 12 months in good-quality studies. For SMBP monitoring plus additional support versus SMBP monitoring alone or with less intense additional support (13 comparisons), low-strength evidence fails to support a difference. Across all comparisons, evidence for clinical outcomes is insufficient. For other surrogate or intermediate outcomes, low-strength evidence fails to show differences. Clinical heterogeneity in protocols for SMBP monitoring, additional support, BP targets, and management; follow-up of 1 year or less in most studies, with sparse clinical outcome data. Self-measured BP monitoring with or without additional support lowers BP compared with usual care, but the BP effect beyond 12 months and long-term benefits remain uncertain. Additional support enhances the BP-lowering effect. Agency for Healthcare Research and Quality.