During the past decades, lung transplantation has been widely introduced as an effective treatment in patient with end-stage lung disease. However, infections and rejection have been the main complicating factors. In this study, we studied the infectious complications in patients who had received lung transplantation in Masih Danehsvari Hospital which is the main center for lung transplantation in Iran between 2001-2008. In a 7-year period, totally, 20 lung transplantations were carried out in our center of whom the transplantation was successful in 13 cases and they survived at least for the first week post-transplant. Having performed the follow-up in this population, overall, 54 episodes of infections were detected and registered. Infectious episodes were studied according to the time of infection (Early: <1 month; Middle: 1-6 months; Late: >6 months post-transplant). The most common involved organ was respiratory system which accounted for 83.3% of infections. Notably, all the infections occurred in the Early period were Respiratory infections. Also, the bacteria were the most common cause prompting infection in all timing periods. According to our findings, there is a special pattern of infections with respect to the culprit causative agents: Elapsing from Early Period toward Late Period, the frequency of viral infections increases while the incidence of fungal infections decreases, so that more than 50% of fungal infections occurred after the first month post-transplant. Moreover, infections due to Aspergillus accounted as 75% of fungal infections. The most common bacteria causing infections in our patients were Pseudomonas, Acinetobacter, and Staph Aureus, in a decreasing order respectively. With regard to detecting the culprit organism, Bronchoscopy with Broncholaveolar lavage(BAL) and tracheal aspirates accounted as the two most frequent routes while they yielded the responsible organisms in 56.2% of infectious episodes. Of the total 54 episodes, the infection was successfully cured in 45(83.3%) episodes. However, of these 13 patients transplantation resulted in death in 7 cases in which the infection was either present concomitantly with transplant rejection (6 cases) or alone (1 case). With regard to the outcomes, fungal infections accounted as the most deadly causes so that mortality occurred in 25% of these infections. Furthermore, 33.3% of Aspergillus infections lead to death and Pseudomonas and Acinetobacter resulted in death in 30% and 28.6% respectively. Surprisingly, the drug resistance was significantly frequent especially in gram negative rods. In conclusion, Infections along with transplant rejection are the most common complications and account as the major causes of death in lung transplantation. Fungal infections, due to their high mortality rate and also somewhat sophisticated treatment should be addressed as important issue in lung transplant recipients. As well, gram negative rods with high degree of drug resistance make the problem complicated. Therefore, implementing preventive measures, efficient infection control, early diagnosis, and appropriate treatment are of importance to obtain favorable outcomes in these patients.