When the raising Holstein calves were pastured from the middle of May to the middle of October in the Ozasa pasture, the level of some serum nitrogenous components was pursued over four years. The level of serum urea, protein, and portein fractions was estimated in time course and the similar tendencies were obtained for the respective components in every pasturing. The changes of the concentrations of serum free amino acids were investigated in the last pasturing.1) The level of serum protein increased gradually from the middle of June to August, and then it tended to decrease very slightly.2) The percentage of albumin fraction increased gradually from the middle of June to July, and then it tended to decrease gradually slightly or to continue constantly. The percentage of γ-globulin fraction tended to increase remarkably until September or October.3) The level of serum urea increased gradually from after one month of pasturing to August, and then it tended to continue constantly or to increase very slightly.4) The increase of the sum of serum free amino acids was found at the middle of June, and the high level continued during pasturing. When the investigation was done for drylot feeding at about one and half months after the end of pasturing, the value decreased to the level which was found at the initial stage of pasturing. This point was very similar to the level of serum urea.It seems that these high level of serum urea and free amino acids reflects high protein and low energy in the pasture plants.