Statistics for The behaviour of class-3 type prestressed concrete beams, at the limit states of cracking, deflexion and collapse are investigated by experiments on pretensioned beams with mild steel as supplementary reinforcement. Several methods of calculating the width of cracks are examined in the light of experimental results and an empirical formula, which includes the effect of percentage of untensioned reinforcement is suggested. The deflexions of beams, based on the method of Beeby and Taylor, were marginally conservative when compared with the experimental results. The ultimate moment capacity of concrete sections with tensioned and untensioned reinforcement, was underestimated by as much as 10, 15 and 25 per cent by the Indian, British and American Code recommendations. © 1973.