Previous studies have shown that injection of antigen into 24 hr cutaneous basophil hypersensitivity (CBH) reaction sites results in immediate degranulation of local basophils and release of mediators, such as histamine, that increase vascular permeability. In the current study, cell counts were made at these antigen-challenged CBH sites, 4, 8 and 24 hr later, and demonstrated a prolonged reduction of basophil numbers following antigen challenge. These results were interpreted to signify that mediators released by degranulating basophils led to inhibition of subsequent basophil accumulation. Local eosinophil infiltration was not inhibited, and in some cases was augmented. Local injection of histamine into CBH sites did not mimic the effect of antigen. It was concluded that one of the factors regulating accumulation of basophils at CBH sites was degranulation of basophils that had arrived previously.