High strengtj buoyancy materials, such as syntactic foam, are required to provide buoyancy for a wide variety of deep submergence vehicles and deep ocean installations. Syntactic foam of 22pcf net buoyancy is currently variable for these applications, together with suitable quality control testing procedures. Materials of 34pcf net buoyancy are achievable based on the development of composites such as aggregates of small hollow spheres embedded in a matrix of syntactic foam. © 1969.