The aim of the present study was to estimate the (co)variance components for the most economically important wool traits in Merino sheep in Uruguay, testing the importance of maternal effects and determining the most appropriate model for each trait. The characters analyzed were greasy fleece weight (GFW), clean fleece weight (CFW), average fibre diameter (FD), coefficient of variation of fibre diameter (CVFD), staple length (SL) and Comfort Factor (CF) (percentage of fibres lower than 30µm) at yearling shearing (12.5 months of age).