Abstract The object of this paper is to present the results of a study formulated for the purpose of testing out methods for the control of poultry diseases under intensive management. The work which follows is a resume of the methods used upon a comparatively large poultry plant, covering about eight acres of ground, with buildings of various types, located at the Massachusetts Agricultural College. A flock of about 1500 laying birds is maintained for the instruction of students and for experimental purposes. It became necessary to control an excessive mortality, which developed gradually, and became most threatening during the fall and winter months. In order to determine the factors related to the mortality, the following methods were adopted; Postmortem examination of the dead and sick birds. Postmortem inspection of some of the birds dressed for market. Frequent inspection of the flocks. Two vicious habits were found to . . .