Twenty single male Assaf lambs were divided into two groups and housed in semi-open barns. Air temperature averaged 35A degrees C. For 9 weeks after parturation, one group was cooled by fan between 1000 and 1600 hours and the other group was not cooled. Rectal and skin (head and testis) temperatures, respiration rate, and pulse rate were recorded twice daily. Lambs were weighed individually every week and levels of T3 and thyroxin were determined. Differences in rectal, head, and testis temperatures (P < 0.05) and respiration rates (P < 0.01) between the two groups were significant. Growth was affected positively by fan treatment, live weight increased by 15%, and cooled lambs had higher thyroxin levels.