Leucopaxillus albissimus var. paradoxus form albiformis (Murr.) Sing. & Sm. (Agaricaceae) is a medium to large, white-spored woodland mushroom occurring on the west coast of North America. Other varieties of the species occur elsewhere. Unlike those of most agarics, carpophores of L. albissimus are remarkably resistant to bacterial decay and persist in the environment for long periods of time. It has been speculated that this is at least in part due to the presence of antibiotic substances (1). Because tryptanthrin, an alkaloid with antibacterial properties (2), has been isolated from Leucopaxillus cerealis var. piceina (3), an investigation of the constituents of L. albissimus var. paradoxus form albiformis seemed to be worthwhile. TIC examination of extracts of the mushroom revealed that a compound with a bright blue fluorescence under uv light was present. This compound, which occurred in the tested specimens at the impressive concentration of 2 g/kg fresh wt, was identified as 2-aminoquinoline on the basis of ¹H-nmr, ¹³Cnmr (4), and mass spectra as well as by comparison with an authentic sample. Although synthetic 2-aminoquinoline has been known since the last century (5), it has heretofore not been reported to occur in nature. This compound possesses an interesting spectrum of biological properties, which include antibacterial (6), protease inhibitory (3, mutagenic (ti), and antitumor (9) activity. In our own investigation, 2-aminoquinoline inhibited the growth of the soil microorganisms Cytopbaga jobnsonae, Streptomyces galilaeus, and Penicillium infhtum. In addition, using the nematode Nippostrongylus braziliensis, we were able to demonstrate that 2-aminoquinoline possesses anthelmintic activity.