Abstract: Hollow microcapsules or solid microspheres for use in diagnostic procedures, as well as methods for making the microcapsules, are provided, which are formed by combining a volatile oil with an aqueous phase including a water soluble material such as a starch, modified starch or proteinaceous material, or a polyethylene glycol (PEG) conjugate, to form a primary emulsion. The primary emulsion then is combined with a second oil, to form a secondary emulsion, and the material is permitted to harden and to form microcapsules around a liquid core of the volatile oil. At least part of the volatile oil then may be removed by evaporation to produce hollow microcapsules. Optionally, all of the volatile oil may be removed prior to hardening of the material, which produces solid microspheres. The The microcapsules can be used in a variety of applications for diagnostic purposes and for drug delivery.