Rituximab use in hematology and oncology practice has significantly and positively improved the clinical outcomes in patients with a wide variety of B-cell lymphoproliferative disorders. However, emerging data reveal that there is a risk of viral hepatitis B reactivation in some patients treated with rituximab. Many of these cases result in treatment delays, inferior oncologic outcomes, increased morbidity, and more rarely fulminant hepatic decompensation and death. Indeed, the rituximab package insert and many clinical practice guidelines have been modified to reflect these concerns. The true incidence and mechanism of reactivation are still being elucidated. This article focuses on the current evidence that supports these recently revised clinical recommendations along with a review of the risk factors for reactivation, suggested monitoring, and preventative interventions.