Synopsis The paper examines the effects of the addition of various fibres, including fibrillated and monofilament polypropylene, as well as round straight, Duoform, crimped and hooked steel, upon the flexural load-deflection properties of a basic concrete matrix at three different ages. The flexural and splitting strengths of the beams were increased with the addition of steel fibres, especially for those with efficient forms of mechanical anchorage, such as Duoform and hooked steel. The fracture toughness of reinforced beams was increased considerably for all the fibres used.