Summary: The skin reaction to echinococcus fluid which is obtained in patients recently suffering from echinococcus disease, is accompanied by circulating antibodies capable of transferring a local sensitiveness to the skin of normal individuals, but not capable of being precipitated by the echinococcus fluid in the test tube. Similarly, the skin reaction to Ascaris extract is likewise accompanied by “reagins” but not by “precipitins.” Hypersensitiveness to Ascaris is not uncommon, and may be acute, even in individuals who give no signs or symptoms of previous infection. These various observations suggest that the intradermal injections of the corresponding extracts may be a method of diagnosis in other forms of helminthiasis, which is worthy of study.