This paper reports the third part of a study carried out to reveal the comparative production performances and effects of some environmental factors on the production characteristics of Chios and Imroz ewes kept in a single flock under semi-intensive conditions. In this report, the effects of some environmental factors on production characteristics are considered. The effects of genotype, sex (except in the case of fleece qualities) type of parturition, the age of the mother and years of birth on the fleece yields and body weights of lambs at different periods and first-shearing (6 months of age) fleece yields were investigated. In ewes, the effects of genotype, age and production years on fleece yield and fleece quality were examined, and the effects of genotype, type of parturition and number of lactation on lactation periods and milk yields and on weights after shearing and before mating were investigated. These effects were generally found to be important, except for: the effects of parturition type on the total lactation period and milk yield; the effect of lactation number on lactation period; the effect of genotype on first-shearing fleece production; the effects of parturition type, the age of the mother and years of parturition on the staple length of first-shearing (6 months) lambs; and the effects of genotype and the age of the mother on the fiber diameter (P