Ozone-induced graft polymerization of hydrogel forming polymers on to polypropylene (PP) membranes and fibres was studied. A higher rate of water absorption and higher water content at equilibrium were found when diethylene glycol methacrylate (DEGMA) rather than 2-hydroxyethyl methacrylate (HEMA) was grafted on to microporous substrates. Ozone-induced grafting of HEMA and DEGMA on to polypropylene fibres resulted only in thin hydrogel layers that were evenly distributed on the fibre surfaces. Dynamic contact angle measurements of HEMA-grafted fibres using water as the test liquid showed a hysteresis typical of a polyHEMA gel. A higher wettability was obtained when DEGMA was grafted on to the PP fibres.