The present study aimed at investigating the effect of high level of feeding and antibiotic growth promoters (flavomycin and monensin) on the wool follicle activities and fibre growth in sheep. Sixty Barki ewe lambs at 4.5 months of age and 20.6 kg body weight were randomly taken from the main flock of Mariout Experimental Station of the Desert Research Center and divided into six equal groups. Five groups were offered a basal diet covering the requirements for growth rate of 100 gm/day. Of these five groups the 1^st was the control, the 2^nd and the 3^rd were supplemented with flavomycin at the rate of 20 and 40 mg/head/day, respectively. The 4^th and the 5^th groups were offered monensin at the rate of  10 and 20 mg/head/day, respectively. The sixth one was given a high level of feeding to cover a growth rate of 150 gm/day.  Treatments continued for eight months. Wool follicle activity and fibre growth were measured using histological and histochemical sections from the skin of the yearling ewes sampled at 12.5 month of age. The treated animals did not show any difference in their first fleece weight. High level of nutrition significantly (p < 0.05) increased the dimensions of both primary and secondary wool follicles. The histochemical analysis showed that the high level of feeding increased carbohydrate concentration, protein content and activity of the alkaline phosphatase enzyme indicating high activity of follicles. In addition, the same treatment led to an increase (p < 0.05) in the diameter of both primary and secondary fibres. Neither wool follicles nor fibres were affected by the administration of both flavomycin 40 mg/head/day and monensin 10 mg/head/day. However, the level of 20 mg/head/day of both two types of growth promoters showed a considrable improvement in the traits under study towards more follicles activity and wool growth. It was concluded that using high level of nutrition or administrating flavomycin or monensin at the rate of 20 mg/head/day would improve wool follicle characteristics in yearling Barki ewes towards increasing their activities.