The postfire mechanical performances of water-cooled full-scale GFRP cellular columns subjected to axial compression were evaluated after exposure to an ISO-834 fire from one side for periods of 60 and 120 mins. The elastic modulus and postfire buckling loads exhibited significant recovery after cooling because of the partial reversibility of glass transition. Existing methods to predict ultimate loads based on experimental buckling curves have proved inaccurate. Ultimate loads were accurately predicted, however, based on a shear failure criterion and by taking large initial imperfections caused by fire damage into account. Recently developed models to predict time-and temperature-dependent material and postfire properties showed good agreement with the experimental results and were thus further validated. DOI: 10.1061/(ASCE)CC.1943-5614.0000191. (C) 2011 American Society of Civil Engineers.