The present paper provides a methodology to analyse the effect of corrosion on the strength and stiffness of the slab-and-girder deck of a road bridge. A linear finite element model of a typical medium span deck of an existing bridge was developed as per the as-built drawings. The vehicular loadings were as per the recommendations of the Indian Roads Congress specifications and the design rating of the bridge. Based on the phenomenon of corrosion, a time-dependent reduction in the area of flexural reinforcement near the soffits of the girders, was considered in the model. The effects of flexural cracking, creep and spalling of concrete were incorporated in the model with non-prismatic section properties and their stage-wise variations. From the analyses of a girder section and the computational model, it was observed that due to corrosion, the allowable moment capacity of a girder falls below the demand under dead load plus the rated live load, within the target service life of the bridge. However, the effect of corrosion on the stiffness of the deck is not substantial to be accurately measured by a conventional sensor. It is recommended that the procedure adopted in the paper can be used by the practicing professionals for numerically assessing longer span decks, to have a’priori estimates of the quantities that can be measured in a field test. © 2012, The Institution of Engineers (India).