BACKGROUND During the past decade, interstitial pneumonia (IP) is one of the newly recognized adverse events regarding rituximab therapy. However, disease characteristics of IP after autologous hematopoietic stem cell transplantation (ASCT) have not been well-described since the introduction of rituximab. METHODS We retrospectively analyzed 103 patients with B-cell non-Hodgkin lymphoma undergoing ASCT. A propensity scoring system was applied in our analysis to eliminate potential confounding factors of covariates. RESULTS The total number of patients who developed IP was nine. Five patients developed IP among 57 patients previously treated with rituximab, and four patients developed IP among 46 who were rituximab-naïve. Cumulative incidence of IP was 7.8% at 1 year. Among the patients using rituximab, one patient had IP during the peri-engraftment period (cytomegalovirus infection), three patients had IP between 3 and 12 months (Pneumocystis pneumonia [PCP, n = 1] and unknown cause [n = 2]), and the other one patient had IP 3.3 years after ASCT (unknown cause). Four patients in the rituximab-naïve group developed IP between 3 and 12 months (PCP [n = 1] and unknown cause [n = 3]). All nine patients had symptomatic episodes before IP, three of which died of IP or secondary infections. Patients receiving a total body irradiation conditioning regimen had a higher risk of IP (odds ratio = 3.6, P < .001), whereas the incidence was not affected by rituximab usage (P = .85, Log-rank test). CONCLUSIONS This study shows that the rituximab usage was not identified as a risk factor of IP and that total body irradiation was the only independent risk factor for IP. Close monitoring is encouraged when symptomatic unexplained episodes are identified during follow-up examinations after ASCT.