The American Gastroenterological Association has issued updated clinical practice guidelines for preventing and treating hepatitis B virus reactivation in at-risk patients. The expert panel made a strong recommendation for high-risk patients (baseline hepatitis B virus reactivation risk over 10%) and a conditional recommendation for moderate-risk (1% to 10%) and low-risk patients (under 1%). Prophylaxis should begin before initiating risk-imposing therapy and continue for at least 6 months after therapy completion (12 months for B cell–depleting agents).