Abstract: Introduction: Prolactin (PRL) is an immune stimulating hormone and may be important in the pathogenesis of some autoimmune diseases, such as SLE. This study was designed to detect the PRL level in patients with Behcet's disease (BD), and its relation to the different manifestations of the disease. Materials & Methods: Thirty-seven new male patients with BD and 29 age matched control normal individuals (CON) was selected as every consecutive patient. The diagnosis was based on the presence or not of the Iran criteria. There were no history of medication or disease affecting the PRL level. Serum PRL was measured by RIA with Amerlex-M kit. The mean level of PRL in each group and subgroups (according to the clinical and paraclinical symptoms) was determined and compared by the student paired t test. Results: The mean PRL level in BD was higher than CON (213+126 Vs 97+53 with a p<0.00003). In BD patients there was no significant relation between PRL level and the disease manifestations, specially the disease duration (p=0.66), ocular (p=0.62) and articular involvement (p=0.73), positive pathergy test (p=0.95), and positive B5 (p=0.11). Conclusion: This is the first report showing an increased level of serum PRL in patients with BD. This may suggest a potential role for neuroendocrine dysfunction via PRL in the pathogenesis of BD. The increased level was shown even in patients with more prolonged disease (>5 years). The increased level was not related to the B5 genetic background as it is for the PMN dysfunction. It was not related to the duration nor to the manifestations of the disease such as the ocular or the joint involvement. Further studies are needed to clarify the role of PRL in the pathogenesis of BD, and the probable beneficial effect of PRL suppression therapy (Bromocriptine) in this disease.