Five different batches of class C20 concrete, containing Dramix-RC-80/60-BN steel fibers (SF's) as additives at doses of 0, 30, 40, 50 and 60 kg/m(3), and six phi15x30 cm prisms were poured from each batch. Standard crushing tests were run on all the specimens and the respective load-displacement and stress-strain curves were plotted. Toughness, ultimate compressive strength and the modules of elasticity were determined for all specimens. The compressive strength and modulus of elasticity declined in 30 kg/m(3) steel-fibre-additive concrete (SFAC) by 9% and 7% compared to the reference C20 concrete without SF's, and the area under the load-deflection curve grew more than two-fold. In concrete with with a higher SF dosage, the differences in strength and elasticity were around 10% whilst toughness was about the same. Because toughness values were similar in 30, 40, 50, and 60 kg/m(3) plain SF- additive concrete and the strength and modulus of elasticity were slightly better in the mixes with the smallest proportion of SF, for reasons of economy, 30 kg/m(3) was taken as the optimum dose of steel fibre to be added to the reinforced concrete used in a second phase of the study. Hence, of the six reinforced concrete (RC) beams made, all of equal size and with the same under-reinforced tensile reinforcement design, three were made with concrete containing the above-mentioned dose of SF. In addition to compressive strength, which was found to be 18% greater for the SFARC beams than the ordinary RC beams, and the upper arms of the load versus mid-span deflection curves prior to ultimate failure of the SFARC beams were considerably longer than the same arms on the curves for ordinary RC beams.