This paper presents the results of a thermal buckling analysis for clamped, rectangular plates based on energy considerations. The analysis reveals that both of the edge length to thickness ratios (a/h, b/h) are independent parameters, i.e. fixing the aspect ratio (a/b) is not sufficient to ensure a unique problem. The results also show that predictable modal groupings and curve veering occur in the eigenvalue loci as the aspect ratio is varied. Accompanying this analysis are a series of experiments to determine the buckling temperature for plates with varying edge length. However? measurements of the critical temperature for flat plates, T-cr(F) are complicated by the fact that initial geometric imperfections are inherent in any real structure. In this case, the pitchfork bifurcation associated with buckling is replaced by a saddle-node bifurcation at T-cr(lm), which is easily measured. An analysis is performed using von Karman plate theory to determine the ratio of T-cr(F)/T-cr(lm) as a function of the initial imperfection size (A) over tilde. Knowing this functional relationship and the measured values of (A) over tilde and T-cr(lm), the flat plate buckling temperature may be determined. Comparisons between the buckling analysis and the experimental results show good agreement. (C) 2001 Elsevier Science Ltd. AH rights reserved.