AbstractIn order to satisfy the serviceability limit states, a concrete structure must be serviceable and perform its intended function throughout its working life. Excessive deflection should not impair the function of the structure or be aesthetically unacceptable. Cracks should not be unsightly or wide enough to lead to durability problems. Design for the serviceability limit states involves making reliable predictions of the instantaneous and time-dependent deformation of the structure. This is complicated by the non-linear behaviour of concrete caused mainly by cracking, tension stiffening, creep and shrinkage. This paper provides an overview of the behaviour of reinforced concrete beams and slabs at service loads and outlines a reliable method for the calculation of deflection.