This research presents an experimental study on the behavior of reinforced concrete specimens with steel fibers submitted to the splitting test and to direct tension. A total of 72 specimens were tested in the LEM-DEC PUC-Rio; 54 specimens with three different diameters and fiber consume for the diametral compression test and 18 with variations of fiber volume fraction for the direct tension test. The 54 specimens were divided into three groups according to their compressive strength (20, 30 and 50 MPa), each group having 18 specimens with variations of fiber volume fraction (20 kg / cubic meter, 40 kg / cubic meter and 60 kg / cubic meter and diameter (5 cm, 10 cm and 15 cm). The purpose was to investigate the tensile stress, the fracture energy and the size effect. The results allowed the analysis of the influence of the fibers and specimen diameter on each variable before mentioned. The tensile stress varies linearly with fiber volume fraction and diameter, and the resistance of the specimens with 15 cm in diameter is 42 per cent less than the resistance of the 5 cm specimen. The fracture energy was not increased significantly with the increase of fiber content from 40 kg fibers / cubic meter to 60 kg / cubic meter. The size effect analysis shows that tensile strength decreases as the diameter increases. These results are similar to those of studies conducted by Carpinteri (1995), even with different values of fiber consume. The 18 specimens submitted to direct tension had the same diameter, varying in resistance (20, 30 and 50 MPa) and fiber volume fraction (20 kg / cubic meter, 40 kg / cubic meter and 60 kg /cubic meter). Here the plastic and elastic deformations were evaluated. The plastic region is not clearly defined for the fiber fraction of 20 kg / cubic meter presenting a behavior similar to the conventional concrete.