A novel manufacturing process of gas-filled. hollow, poly-butyl-2-cyanoacrylate (PBCA) microspheres in an aqueous phase is the subject of this paper. The two-step process enables the control of the particle-wall size. as well as the particle size. Particles of this type are useful in the medical and pharmaceutical industry for diagnostic purposes in connection with ultrasound and for life or food science applications, such as taste masking, release on demand, etc. Depending upon the process conditions. the particle size ranges from I to 5 mu m. The microparticles are formed by using surfactant-stabilized microbubbles, which act as a template. At the interfacial area of these templates, PBCA nanoparticles create deposits that form the particle wall, as the result of a partial filming process. The density of the particles has been calculated as ranging from 100 up to 300kg/m(3) and the Volume fraction of the entrapped gas can be 5% or more. The developed process can operate on a scale of several kilograms. (c) 2006 Elsevier Ltd. All rights reserved.