In 2 series of attempts to influence the sex ratio in cattle by fractionating sperm by Schilling's method of sedimentation, results were inconsistent. Sperm collected weekly from 8 bulls in the 1st experiment and from 15 in the 2nd were frozen. Thawed specimens having a motility of at least 4 and concentrations of at least .5 x 109 sperm per ml were allowed to sediment for 1 hour in Schilling's medium. Fractions designated as A (very heavy), B (heavy), C (medium), and D (light) gave the following sex ratios in 543 artificial inseminations: A, 118 males/100 females; C, 107; D, 146 (all nonsignificant vs. 106 males/100 females in theoretical controls). In the 2nd series of 2230 experimental artificial inseminations and 862 controls, there were 113 males/100 females from Fraction A, 135 from B, 100 from C, and 110 from D, compared with 122.5 in controls (all nonsignificant). These 2 sets of results were neither significantly different nor consistent, since the 2 highest ratios were obtained from light and heavy fractions.