In a study of two coarse wool breeds (Awassi and Karadi) and their reciprocal crosses, data were obtained on the mean fibre length, mean fibre diameter, fibre type ratio, medullation and on the effect of some environmental factors on these traits. Reciprocal crosses showed intermediate values, in growth rate of fibres, percentages of fibre types and medullation, between those of the parental breeds. Sex exhibited a significant effect at weaning only, on fibre length. Heterosis in fibre length, at the two ages, was small and negative. Maternal influence on fibre length was small and not significant. Fibre length in Karadi sheep showed the highest frequency of bimodal distribution whereas Awassi showed the lowest. Awassi × Karadi was closer to Karadi and Karadi × Awassi had greater affinity to Awassi in the frequency of samples showing bimodal distribution.
Reciprocal crosses had larger diameter, at weaning, than those of the parental breeds. At 1 year of age they assumed an intermediate position between the pure bred parents.
At weaning, the two reciprocal crosses showed a highly significant heterosis in fibre diameter; its value decreased with advancing age and it showed no significant effect at 1 year of age.
Maternal influence on fibre diameter was very small and not significant.
Karadi × Awassi and Karadi samples had the highest percentage of samples showing bimodal distribution of fibre diameter.
Samples with bimodal distribution of both length and diameter, indicating two coats, had the highest frequency in Karadi followed by Karadi × Awassi; Awassi showed the lowest value.
Percentages of fine, coarse and kemp fibres were significantly affected by breed and age of dam. Type of birth showed a significant effect only on percentage of coarse fibres.
Karadi wool might be more suitable for carpet manufacturing. It excelled the other groups in the bimodal distribution of both length and diameter as well as in medullation. Cross-breeding increased the bimodality of fibre distribution.