This study was carried out in the Poultry Experimental Farm of Animal production Department, Faculty of Agriculture, Al-Azhar University, Assiut Branch, Egypt. It amid to study the effect of continuous and intermittent high ambient temperature on growing males of Gimmizah and Golden-Montazah chickens performance from 4 up to 16 weeks of age. A total of 96 male chicks 4 weeks old, were randomly classified to three equal groups each of them 16 Golden-Montazah and 16 Gimmizah. The chicks in the first group (control) were daily exposed to normal conditions. The chicks in the second and third groups were daily exposed to continuous and intermittent high temperatures (35°C) for 5 hours, respectively. All chicks were housed on a partition of floor pens and reared under normal environmental poultry house and daily exposed to 16 continuous lighting hours. All chicks were fed ad-libitum on a commercial standard starter diet.                                                                The obtained results revealed that the Golden-Montazah was significantly higher body weight (p < 0.05) compared to Gimmizah. Whereas, daily weight gain between both strains were not differed. Body weight and body weight gain for chicks exposed to intermittent heat cyclic decreased significantly as compared with control and continuous heat cyclic. Daily feed consumption was significantly (p < 0.05) affected by strain, heat cyclic and their interactions, while feed conversion ratio was insignificantly by strain and heat cyclic just during the periods from 4-12 and 12-16 weeks of age. Carcass cutup parts and hematological parameters were not affected by strain, heat cyclic and their interaction. Liver and testes percentages were significantly affected by strain, while heart and thymus were significantly affected by heat cyclic. The total protein, GPT, T3 and T4 concentrations were significantly affected by strain, heat cyclic and their interaction. Phosphorous, T3 and T4 concentrations were significantly increased in Golden-Montazah compared with Gimmizah. Thus, it could be concluded that the Golden-Montazah more tolerant to high temperature compared to Gimmizah under Upper Egypt climatic conditions.