The optical activities and rotatory dispersions of cholic, deoxycholic, glycocholic and taurocholic acids and their alkali salts were detd. Cholic acid: in alcohol [[alpha]]5893 = 35.07[degree], in acetic acid 37.52[degree], in acetone 37.94[degree], in chloroform, 24.11[degree], independent of the concn. Na cholate in water (15%) [a]5893 = 28.80[degree], increasing with decreasing concn. Deoxycholic acid: [[alpha]]5893 in alcohol 55.56[degree], in acetic acid 55.06[degree], in acetone 55.99[degree], in chloroform, 44.21[degree], independent of the concn. Na salt in water (5%) [[alpha])5893 = 45.40[degree], increasing with decrease in concn. Glycocholic acid in alcohol (10%) [a]5893 = 31.85[degree], Na salt in water (15%) 24.29[degree] both increasing with decreasing concn. Taurocholic acid in alcohol (1.64%) [[alpha]]5893 = 28.74[degree], Na salt in water (5%) 21.65[degree]. Not only the specific rotations but also the rotatory dispersions were very similar in alcohol, acetone and acetic acid. In chloroform the rotations were lower and the dispersions higher. The rotations of the Na and the K salts showed only min. differences. The dispersions of the different acids were similar. The activities of the salts were slightly influenced by other electrolytes. The increase of the activity of the salts with decreasing concn. was much larger below a certain critical concn. different for the different acids (0.75-2.0%).