1. In order to determine the relation of pituitary weight to body weight in the female rabbit, data were collected from 48 female rabbits. These data appear to fall on a straight line when the logarithm of the pituitary weight is plotted against the logarithm of cleaned body weight, and a straight line was fitted using the formula y = axk. The value of the constant k was found to be 0.61.
2. From the data from 31 male rabbits a straight line was obtained by the same formula. The value of the constant k was found to be 0.57 as compared with the value 0.55 obtained by Robb for male rabbits.
3. The growth rate of the pituitary does not show any marked difference after puberty in male and female rabbits as has been recorded for the rat (Hatai).
4. Ten female rabbits were killed at varying periods after copulation and the relation of pituitary weight to body weight examined. No change in the relative size of the pituitary was detectable by the methods used, and it is concluded that any change in weight of the pituitary following copulation, if it occurs, must be slight.