This note is concerned with the H-infinity analysis and synthesis of linear distributed delay systems. An efficient stability and L-2-gain criterion Is established. It is based on a recent approach to the analysis and design of linear time delay systems which represents the system in an equivalent descriptor form. The obtained criterion is used to derive an efficient state-feedback control design which stabilizes the distributed delay system and achieves a guaranteed disturbance attenuation level in spite of a polytopic uncertainty in the system parameters. The new method is applied to the robust stabilization and control of combustion in rocket motor chambers.