Improvements in the processability of polypyrrole-a relatively air-stable organic conducting polymer-can be obtained by producing colloidal dispersions. The particles reported here are ''inside out'', i.e., micrometer-sized, sterically stabilized polystyrene latex particles are coated with an outer layer of polypyrrole. Their synthesis and physical properties are described and ideas for further work and potential novel applications, for example in immunodiagnostic assays, suggested.