Buckling of laminated composite thin walled rectangular box beam configurations has been studied. The increasing use of composite materials in the construction of aeronautical and civil engineering structures has generated a special interest in the analysis of elastic stability of laminated composite structure subjected to inplane loadings. The effect of number of layers, lay-up sequence and fibre angle on the buckling load is studied for symmetric and anti-symmetric lay-ups.Buckling of laminated composite thin walled rectangular box beam configurations has been studied. The increasing use of composite materials in the construction of aeronautical and civil engineering structures has generated a special interest in the analysis of elastic stability of laminated composite structure subjected to inplane loadings. The effect of number of layers, lay-up sequence and fibre angle on the buckling load is studied for symmetric and anti-symmetric lay-ups.