Nine healthy and seven mite-sensitive allergic subjects were examined by skin sensitivity and IgE antibody to fractions from Dermatophagoides farinae, including high and low allergenic fraction to human. In the intracutaneous test, all healthy subjects reacted to 200 ng and in particular, five of them to 0.2 ng of Fr void on Sephadex G-100 filtration which was a low allergenic fraction. Furthermore, end points of intracutaneous test and specific IgE antibody titers did not correlate on Fr void. Conclusively, Dermatophagoides farinae extracts contain a nonimmunologically highly skin-reactive fraction.