Systemic reactions to Hymenoptera venoms require an allergological work-up before starting venom specific immunotherapy (VIT) in order to prove an IgE-mediated reaction and identify the culprit insect venom. In addition to skin tests and the determination of specific IgE antibodies, the basophil activation test (BAT) using flow cytometry has developed into a powerful test and sensitive marker for this purpose in recent years. Compared to the other tests, the BAT seems to have a better informative value in terms of clinical relevance. In Hymenoptera venom allergies, BAT is particularly useful for the diagnosis of cases with unclear or contradictory history or sensitization profile. Its results are related to adverse reactions during immunotherapy and its efficacy. They therefore have a certain predictive value for side effects and treatment success of VIT. In research, BAT is mainly used to characterize the allergenic components of Hymenoptera venoms. This review article focuses on these topics.