We have designed a human basophil degranulation test based on a one-step method of basophil staining after exposure to a specific allergen. This very simple test is now commercially available as a ready-to-use kit. It explores the allergic sensitivity at the cellular level, probably through IgE-dependent sensitization of the basophil. It positively correlates with histamine release and radioallergosorbent test (RAST). It detects sensitivity to common allergens and to chemical and food products as well. In its present state, the test provides a simple, inexpensive specific means for in vitro diagnosis of allergic diseases. Recently, it has been further developed to be performed on the automatic Hemalog D Technicon machine.