This paper presents a comparison of the properties of concrete slabs when two types of fibres are added. One specimen had no fibres and acted as a control specimen. The remaining four specimens had steel and polypropylene fibres added in the volumetric ratio of 0.5% and 1.0%. The dimensions of the slab specimens were 820Ã820Ã80 mm and were supported by four rollers at their edges. A displacement controlled point load was applied at the centre of the slabs. The ductilities of the tested slabs were calculated and compared so as their load carrying capacities. Results of the experimental programme were compared with theoretical predictions. Based on the results of the experimental programme, it can be concluded that the addition of 1% by volume steel fibres had the best effect on the ductility of the slabs.