Aureobasidins A to R were isolated from the fermentation broth of Aureobasidium pullulans R106. Aureobasidins are cyclic depsipeptide antibiotics with MW's ranging from 1,070 to 1,148. Aureobasidins showed high in vitro antifungal activity against Candida albicans. In the course of our screening for antifungal substances from various microorganisms, new antifungal antibiotics that we named aureobasidins were obtained from the fermentation broth of a strain of Aureobasidium pullulans, a species of black yeast. The producing organism, strain R106, was isolated from a leaf collected at Tsushima in Nagasaki, Japan. In this paper we describe the taxonomy of the producing organism, the production and isolation procedures of aureobasidins A to R, and their physico-chemical and biological properties. The structural studies of aureobasidins A to R will be described in the following papers.