Fermented milk drinks (liquid yogurt) produced by 7 different domestic manufacturers between the end of Aug. 1978 and the middle of Feb. 1979, were tested for microbiological and physico-chemical properties. 1) Single Lactobacillus strain has been used by all manufacturers and L. bulgaricus was found in 3 products, L. casei in 2 products, L, helveticus in 2 products. 2) At second day after bottling, the numbers of lactic bacteria ranged from 65×10^7 to 1.4×10^7 per ㎖. of the 6 products, and one product contained 3.5X105 per ㎖. 3) Except one product, every product had more than 10^7 lactic bacteria per ㎖. at 5℃ for 5 days. 4) No Coliform bacterium was detected in all samples. 5) Yeasts, molds and spores were detected in larger numbers in Aug., Oct., Sept., than in Jan., and Feb., and one manufacturer put especially more yeast s and sept., than in Jan., and Feb., and one manufacturer put especially more yeasts and molds, and another had more spores. 6) The mean pH values of the products were between pH 3.23 and pH 3.78. Titratable acidifies were found to be between 0.4102 and 0.5927%. Refractive indexes varied between 1.3541 and 1.3650. 7) Total solids contents were between 16.16 and 22.19% ; ash, 0.51∼0.32 protein, 0.50∼1.32%; monosaccharide, 1.26∼3.62% Roducing sugar, 10.27∼15.85%. 8) Further researches are needed on nutritional and microbio logical improvements of the liquid yogurts, and also on the function of lactic acid bacteria for the promotion of human health. 9) Product $quot;G$quot; has been known to be the best in micsobiological and physico-chemical qualities.