Abstract : The present research is devoted to study the behavior of RPC beams subjected to pure torsion, the torsional toughness of RPC beams, and proposed analytical model to estimate the torsional moment of RPC beams. The experimental work of this research which includes examined ten RPC beams includes both solid and hollow beams in torsion, the main variables in this research are focused on the influence of the hollow RPC beams which includes (shape, location, and dimension) and effect of the transverse and longitudinal reinforcement ratio on the ultimate torsional moment of the tested beams. This study showed the effect of hollow RPC beams in reduction the cracking and ultimate torque and also torsional toughness when comparing with solid RPC beams. The experimental results showed the influence of spacing between stirrups and longitudinal bars in torsional moment of RPC beams. The cracking and ultimate torque of RPC beams improved when decreasing spacing between stirrups. While the longitudinal bars have been not significant effect on the torsional strength of the RPC beam. In this research, the torsional behavior of RPC beams is theoretically predicted from utilizing regression analysis non-linear by computer program SPSS. Furthermore, when compared to experimental results, the findings produced from an analytical model of RPC beams proposed show good agreement.