The chemotherapy treatment of non-Hodgkin's lymphoma(NHL)is associated with an increased risk of infection because of the intensity of the treatment. We examined the frequency of herpes zoster infections in 170 non-Hodgkin's lymphoma patients who had completed a chemotherapy course. Furthermore, we examined the risk factors contributing to these infections. This study took place in the Department of Hematology at Ogaki Municipal Hospital. Of the 170 patients treated in our facility, 25 developed herpes zoster(14. 7%), 19 of whom developed symptoms within 30 days of starting the chemotherapy treatment. Significant risk factors for the development of herpes zoster were post-autologous peripheral blood stem cell transplantation, relapsing patients, ten or more total treatments and the use of two or more regimens. In these cases the average interval of the treatments had to be extended from 6. 6 days to 14. 2 days due to the infection(comparing post - infection to pre-infection). We recommend the prophylactic use of low-dose acyclovir in patients with a higher risk of herpes zoster infection. We also recommend further monitoring of other opportunistic infections associated with chemotherapy usage.