Background: Hepatitis B virus (HBV) affects over 250 million people worldwide. Most people with chronic HBV (HBsAg positive) have no signs or symptoms of infection. However, when exposed to immunosuppression they are at risk of HBV reactivation which can cause hepatitis, liver failure and death. The risk of HBV reactivation in patients receiving chemotherapy for solid tumors, the efficacy of antiviral prophylaxis, and the clinical impact of HBV reactivation in this setting are uncertain. Primary Aim: To estimate the risk of clinical HBV reactivation (increased HBV DNA + transaminitis) among HBsAg-positive patients administered chemotherapy for a solid tumor. Secondary Aims: To estimate the efficacy of anti-viral prophylaxis and the risk of death from HBV reactivation in patients receiving chemotherapy for solid tumors. Methods: A systematic review and meta-analysis of the English language literature on HBV reactivation was completed (OVID Medline, 1946 to Aug 2013). All citations were reviewed by two or more authors. Data from patients with hematologic malignancies were excluded. Pooled probabilities of HBV reactivation risk, death from HBV reactivation, and odds ratio for the impact of anti-viral prophylaxis were estimated with a random effects model. Results: 2,667 citations were identified; 19 were eligible for inclusion. The pooled estimate for clinical HBV reactivation in HBsAg-positive patients receiving chemotherapy for a solid tumor was 21.9% (95% CI; 16.5% to 27.3%) in those not receiving anti-viral prophylaxis, and 2.4% (95% CI 0.7% to 4.2%) in those receiving anti-viral prophylaxis. The odds ratio for clinical HBV reactivation with antiviral prophylaxis compared to no prophylaxis was 0.12 (95% CI 0.06 to 0.25). In the absence of viral prophylaxis, the risk of dying from HBV reactivation in HBsAg-positive solid tumor patients was estimated at 1.3% with a 95% CI of 0.3% to 2.3%. Conclusions: Patients with chronic HBV who are administered chemotherapy for a solid tumor appear to be at substantial risk of clinical HBV reactivation; this risk may be mitigated by anti-viral prophylaxis. In the absence of anti-viral therapy, patients may experience a small but important risk of dying from HBV reactivation.