The bacterial and yeast flora of five lakes-Kroner Lake, a meltwater pool, Relict Lake and two unnamed lakes-on Deception Island in Antarctica were examined. During the sampling and isolation, special care was taken to ensure that the micro-organisms never experienced a temperature above 10 <latex>$^\circ$</latex>C. Gram-negative, rod-shaped bacteria predominated in all of the lakes; Kroner Lake also contained large numbers of Gram-positive cocci. Yeasts were isolated from three of the lakes. An examination of the temperature characteristics of the predominant micro-organisms from the lakes showed that over three-quarters had optimum temperatures for growth below about 20 <latex>$^\circ$</latex>C, while a third had maximum temperatures of about 20 <latex>$^\circ$</latex>C. None of the thirty-one bacteria tested fermented lactose, raffinose or sucrose. Two strains fermented glucose, and one each glycerol and salicin. Several of the bacteria from Kroner Lake utilized compounds that may have been produced by the decomposition of algae in the lake.