We have used a combination of centrifugation onto electron microscope grids and negative staining to study the structure of isolated mammalian centrioles. The technique relies on visualisation of structural detail by use of a goldthioglucose negative stain. The approach provides an easy structural definition of the mature and immature centriole and has revealed some novel proximal projections on the mature centriole. The rapid technique should prove of use in future analyses of centriolar structure and biochemistry. (C) 1996 Academic Press