In the light of the technical experience obtained on the three different kinds of fiberglass reinforced plastic (FRP) rocket chambers for Lambda and Mu rockets developed in the Institute of Space & Aeronautical Science, a cylindrical FRP chamber for Kappa rockets was developed and launched successfully in the second stage motorcase of the K-10-8 rocket in September 1972. The chamber consisted of fiberglass/epoxy composite and was fabricated by a helical filament- winding technique. It had a 420 mm diameter and was 1800 mm in length. The structural weight of the FRP chamber was approximately 70kg and a weight reduction of 27kg was obtained compared with the previous steel chamber. This fact contributed to the high flight performance. The progress of the FRP chamber development research on flexural stiffness necessary for avoiding divergence, burst strength due to internal burning pressure, heat-resistance to aerodynamic heating, joining technique with adjacent stages and so on are described in the present paper, The experimental results on structural tests and test firings on the ground are also included.