RESUMENPara establecer la participacion del tiroides y las adrenales en la Ascitis hipoxica de los pollos de engorde y complementar estudios previos sobre la respuesta cardiohepatica, se realizaron estudios histomorfometricos en 18 pollos sanos y ascIicos Arbor Acress, de diferentes edades. El corazon, higado y adrenales de los animales asciticos, aumentaron su tamano y peso (P < 0.01), se presento hiperplasia cardiaca. Los foliculos tiroideos de animales asciticos presentaron un coloide uniform e, no vacuolizado, acidofilo en ocasiones ausente, comparado con la basofilia y vacuolizacion del coloide de los sanos. Hubo disminucion en la altura del epitelio folicular de los enfermos (P < 0.01). La hipoxia, el frio y el alto contenido energetico de las raciones, pueden actuar aislada o sinergicamente para inducir una hipoactividad tiroidea en animales susceptibles. SUMARYTo study the role o f the th yro id and the adrenal glands in the Hypoxic ascites (one type o f chick edema disease) in broilers, and complement previous studies on the heart and liver, histomorphometrical studies were performed in A rbor Acress broilers o f different ages; 18 healty chicks and 18 w ith ascites. The weight and size o f the heart, liver and adrenal glands, were higher in the sick animals than in the control ones. (P. 0.01).There was cardiac hyperplasia. The thyroideal follicles o f the sick animals, presented uniform, non vacuolized and acidophilic colloid, sometimes to ta lly absent compared with the basophilic and vacuolized colloid o f the controls. It was observed th a t the follicular epithelium was much lower in the sick animals than in the controls (P. 0.01). Hipoxia, cold and energetic feeds could act sinergistically or individual to induce thyroideal hypoactivity in susceptible animals.