Background.: It has been suggested that the frequency and severity of allograft rejection may be related to the degree of allograft ischemia. The purpose of this study was to determine whether ischemic insult correlates with lung allograft rejection. Methods.: Forty-eight left lung transplants were performed from Lewis donor rats into F344 recipient rats. Allografts were divided into two groups based on the degree of ischemic insult. Transplantation was performed immediately (group 1, minimum injury) or after 18 hours of cold (1°C) preservation (group 2, severe injury). allografts were evaluated radiographically based on aeraction scores (0 = opaque to 6 = normal). Animals were randomly sacrificed on days 7, 14, or 21 for histologic and immunohistochemical evaluation of rejection. Results.: On postoperative day 3, significantly lower aeration score was demonstrated in group 2 (3.69 ± 1.71) compared to group 1 (5.0 ± 1.09) (p < 0.05) as a result of the difference in reperfusion injury. However, by day 7 and thereafter, there was no significant difference. Histologic rejection was presented by day 7 and peaked at day 14 with no significant difference between groups. There was also no difference in CD4+, CD8+ infiltrating lymphocyte population or expression of class II major histocompatibility complex antigen on bronchial epithelium. Conclusions.: We conclude that ischemic injury in rat lung allograft does not correlate with the onset or severity of rejection.