Seventy-two subjects have been tested by skin-test (ST) and human basophil degranulation test (HBDT) with grass pollen extract (GPE). HBDT was done, using a suspension enriched in basophils, by a technic on slide. Results are expressed by an index (DI) which is percentage of basophils having apparently disappeared (i. e. degranulated) in presence of GPE. No less than 100 intact basophils (and often many more) were always counted in absence of GPE (control) for each subject, so that DI higher than 35% are significant (p less than 0,001). DI were higher than 35% in 28 positive ST subjects for at less one of three dilutions of GPE (10(-4), 10(-6), 10(-8)); in the 5 subjects with false-negative result, 3 had a weak ST response. In 39 subjects with negative ST, DI were higher than 35% in two subjects and only for one dilution (10(-4)). So, concordance of results of HBDT and obviously positive ST reaches 94%. In 33 positive ST subjects, a significant correlation appears between DI (at 10(-4) and 10(-6)) and flare diameter and between DI (at 10(-4)) and wheals diameter. HBDT appears to be a suitable and simple technic for routinely study of reaginic allergies.