Moment redistribution in beams has traditionally been considered as an ultimate limit state (ULS) phenomenon closely associated with considerations of reinforcement ductility. This paper demonstrates that a significant proportion of this redistribution will almost always occur at the serviceability limit state (SLS) because of the mismatch between the flexural stiffnesses assumed when calculating moments for the ULS and those actually occurring at the SLS due to variations in the reinforcement layout along the member and the influence of cracking. This is demonstrated analytically in the paper and comments are made concerning the current recommendations in BS 8110 concerning member stiffness. Tests on 33 two-span beams are then presented, parameters investigated being values of redistribution, beam depth, reinforcement arrangements, concrete strength and the effect of brittle reinforcement. The results confirm that there is significant redistribution at the SLS and that there is scope for increasing the permissible limits for redistribution beyond those currently prescribed in design codes. This is supported by further modelling although it is shown that considerations of crack width may become a limiting factor.