The thermo-oxidation resistance and weatherability of' LDPE and HDPE compositions, containing up to 45 wt. $6 calcium carbanate, are investigated. The thermo-oxidation resistance is inrestigated by dynamic D'FA and natural ageing is carried out in an exposure station in a seaside climate. The change in strength and colour after ageing is determined. The behauiours of filled and unfilled polymers are compared. Empirical equations are given, describing the change in the investigated parameters during natural ageing .