This paper is concerned with the experimental and numerical study of stiffened laminated composite plates exposed to a normal blast shock wave. For this purpose a detonation is developed from the reaction of LPG-O-2 mixtures in a long circular cylindrical shock tube. The detonation wave goes through into the atmosphere from the open end of the shock tube and acts as a blast load on the stiffened laminated composite plate which is placed in front of the detonation tube. Mounting of the target plate on a steel frame is designed with the object of providing clamped boundary conditions. The air blast pressure distribution is obtained by the use of quartz crystal pressure transducers placed on the wooden model. Strains are measured at the different points on the stiffened laminated composite plate and stiffener. In the experiment and analysis two different load cases are examined. Furthermore, a finite element modelling and analysis of the blast loaded stiffened composite plate are presented and the numerical results are compared with the experimental ones. An agreement is found between the experimental and finite element results in both linear and non-linear ranges. A good prediction is performed for the peak strain in the plate. However a discrepancy is shown between the measured and predicted strains on the stiffener because of the adhesive layer between the plate and stiffener. Prediction of the response frequency that has a great importance in the dynamic phenomena correlates well with the experimental results. The effects of stiffener and loading conditions on the dynamic behavior are examined. Large deformation effects are taken into account for the second loading condition. (C) 1999 Academic Press.