Bronchiolitis obliterans syndrome (BOS) is a common occurrence following lung transplantation and is one of the most important impediments to long-term graft viability. Cytolytic therapy has been used as treatment for BOS, but there is little data documenting efficacy. Furthermore, these agents have been associated with significant adverse effects. Charts of 15 patients who received an antilymphocyte preparation (ALP) for BOS were reviewed. Forced expiratory volume-1 second (FEV1) and stage of BOS were compared before and after treatment. Complications of ALP were recorded from the charts. Two of 15 patients had an improvement in FEV1, 5/15 exhibited no change, and 8/15 continued to decline. There was no pattern associating stage of BOS with likelihood of response to ALP. All patients received antimicrobial prophylaxis and did not experience infectious complications following administration of the ALP. ALP for the treatment of BOS results in an arrest or improvement of FEV1 in approximately 50% of patients. Infectious complications are uncommon when antimicrobial prophylaxis is administered.