Background: Plasma-derived C1 inhibitor (C1-INH) concentrate is a treatment option for acute hereditary angioedema (HAE) attacks and is considered the standard-of-care in many countries, although it is not yet available in the United States. Studies are still being conducted to establish its safety and efficacy as required by the FDA. Objective: To review the medical literature to determine if C1-INH concentrate is a safe and effective treatment for acute HAE attacks. Methods: The following keywords were searched in PubMed and OVID: C1 esterase inhibitor, C1-inhibitor, C1 inhibitor, and hereditary angioedema treatment. English-language articles were searched from 1966 to the present to look for studies demonstrating the efficacy and the safety of C1-INH concentrate. Results: The English-language literature search revealed several studies showing significantly improved relief of HAE symptoms with the administration of C1-INH concentrate – many studies demonstrated some improvement of symptoms within 30 minutes. Side effects have been similar to placebo, and no proven cases of viral transmission have occurred in over 20 years. Conclusion: C1-INH concentrate appears to be a very safe and effective treatment option for HAE.