Alopecia areata is an autoimmune disease characterized by non-scarring hair loss in single or multiple areas of the scalp, face or body. Human beta-defensin 1 is a protein that in humans is encoded by the DEFB1 gene. Defensins form a family of microbicidal and cytotoxic peptides made by neutrophils. Human beta defensin 1 was purified from hemodialysate fluid, but its tissue sources were not identified. Aim:To evaluate serum level of human beta defensin 1 to reveal its role in alopecia areata pathogenesis and to relate with studied clinical parameters. Patients and methods: This prospective casecontrol study was included fourty patients with AA (Group A) and fourty age and sex matched apparently healthy subjects as a control group (Group B). Patients were selected from the Dermatology outpatient clinic of Benha University Hospitals in the period between December 2018 and June 2019. Results:we found that AA group showed no significant difference in serum level of HBD-1 when compared to control group (p=0.03). HBD-1 concentration was not considered as predictor of AA.Conclusion: HBD-1 concentration was not considered as a predictor of AA susceptibility and severity.