A slow and controlled freezing method has successfully preserved the viability and cultural characteristics of fungi that did not survive when they were preserved by freeze drying (lyophilization). The ultra-low-temperature storage did not affect the genetic composition of the frozen materials. Organisms chosen for the studies were: Rhizoctonia solani, R. microsclerotia (Mycelia Sterilia); Botrytis paeoniae (Fungi Imperfecti); Pythium aphanidermatum f. spec. paeoniae, P. debaryanum, Phytophthora infestans, Phy. cinnamomi, Phy. palmivora, Syzygites megalocarpus, and Choanephora cucurbitarum (Phycomycetes). With the freezing apparatus described by Hauschka, the average temperature drop from 0[degree]to -25[degree]C in 15 tests was 1.7[degree] per minute. It required 45 minutes to complete one run. The test organism was suspended in 10% glycerol. Two-tenths ml of suspension was transferred into a Pyrex vial and sealed off with a "Bernz-O-Matic" propane torch. After freezing, frozen samples were stored in a liquid nitrogen (-185.5[degree] to -195.5[degree]C) tank. Samples were thawed in a constant-temperature (37[degree]C) water bath after 3 days'' storage. Viability was recovered when growth appeared on appropriate media after transfers were made from opened vials.