Improvements in concrete technology, reinforcing systems and manufacturing enable the use of longer reinforced precast concrete girders, contributing to the competitiveness of this solution for bridge decks. The weight of the girders should be limited in order to achieve an optimum between span length, transportation costs and lifting costs. The current tendency in design is to minimize the width of the flanges of the girder. This makes the element more flexible to lateral deformation and increases the risk of lateral instability in temporary situations without lateral supports. This is reflected in an increment of the number of accidents and damages associated with such phenomenon. The main objective of this study is to describe a real case study of lateral instability of a 46¿m long prestressed concrete girder during lifting operations as well as to perform a parametric study to understand the limits of the problem observed. In addition to presenting the case study, simplified formulations and numerical simulations are used to assess the safety margins against lateral instability. Special attention is paid to the evaluation of the provisions gathered in codes and guidelines regarding the lateral stability since they might not cover extreme cases.