Leucopaxillus albissimus var. paradoxus form albiformis is a medium to large, white-spored woodland mushroom occurring on the west coast of North America. Its carpophores are remarkably resistant to bacterial decay, which is speculated to be due in part to antibiotic substances. Since tryptanthrin, an alkaloid with antibacterial properties, has been isolated from Leucopaxillus cerealis var. piceina, an investigation of the constituents of L. albissimus var. paradoxus form albiformis was carried out. TLC examination of extracts revealed a bright blue fluorescent compound present at 2 g/kg fresh wt, identified as 2-aminoquinoline on the basis of ¹H-nmr, ¹³C-nmr, mass spectra, and comparison with an authentic sample. Although synthetic 2-aminoquinoline has been known since the last century, it has not been reported to occur in nature heretofore. This compound possesses biological properties including antibacterial, protease inhibitory, mutagenic, and antitumor activity. In this investigation, 2-aminoquinoline inhibited the growth of soil microorganisms Cytophaga johnsonae, Streptomyces galilaeus, and Penicillium infestans. Additionally, using the nematode Nippostrongylus braziliensis, it was demonstrated to possess anthelmintic activity.