Significance of environmental and ewe bloodline effects, and their estimates, on post weaning (PW) fleece traits recorded in a central test sire evaluation flock were investigated. The findings that heavier fleeces were produced by single-born or single-reared or older animals, were generally similar to those reported for yearling expressions of clean and greasy fleece weights. Apart from sex significantly influencing each of the fleece quality traits, mean and coefficient of variation of fibre diameter, staple length and staple strength were largely unaffected by the environmental effects. Significant ewe bloodline and sire X ewe bloodline effects indicate that sire X genotype interactions are important for early age fleece traits. At present, these interactions are partially accounted for by fitting sire X flock interactions in the methodology applied in the MERINOSELECT genetic evaluations.