ACTH in vitro produces non-specific crop-sac epithelium response. Crop-sac maintained in 10 IU.ACTH in isologous serum at 37 degrees C for 6 hrs. showed an increase of 105 +/- 0.95 mg for 12 hrs. 115 +/- 1.13 mg, for 18 hr. 125 +/- 0.95 mg. and for 24 hrs. 145 +/- 2.31 mg. The results were analyzed statistically by ANOVA technique. A significant rise in mean weight. In ACTH treated crop-sac, indicates a time related relationship (P < 0.01, ANOVA, Table 2). Thus present data indicates that there is a correlation between the epithelial response and initiation of ACTH present in the serum.