ABSTRACT Background Rituximab containing regimen has improved the outcome of B-cell lymphoma. One of the problems of rituximab-related infection is latent virus reactivation, for example, hepatitis B virus and JC virus. However, the possibility of increasing the susceptibility to varicella is unknown. In several rituximab using trials, an increase in the community-acquired infection has not been reported. Here, we report a cluster case of varicella patients treated with rituximab containing chemotherapy. Case report We diagnosed four cases from 18 May 2011 to 19 June 2011. All patients were diffuse large B cell lymphoma patients treated with rituximab containing regimen. These patients were hospitalized in two hematological wards and each patient stayed different room. When we diagnosed varicella, we moved the patient to negative pressured room and started universal precautions. All patients were treated with acyclovir. Three mild patients had treated for 7 days. Another severe patient had treated for 5 weeks. We examined anti-VZV antibody in prechemotherapy serum and all those represented post-infection pattern. We analyzed VZV DNA sequence in gene 62 which has diverseness, and all sequences were the same. Therefore, we deduced that they were infected with identical VZV. Conclusion Rituximab has possibility of increasing the reinfection of varicella.