New totally porous, spherical silica particles of <10 µ are shown to be superior column packings for high-performance liquid chromatography (LC). These porous microspheres are prepared in narrow particle size ranges and have been used for liquid-liquid, liquid-solid and exclusion chromatography since both the overall size and internal porosity can be selected and closely controlled. High-efficient columns of these particles are conveniently prepared by a high-pressure slurry-packing technique using stabilized aqueous suspensions. Performance of columns of these microspheres are the highest yet reported, with 5–6 µ, particles producing 23 effective plates per second for solutes with capacity factors, k′ = 12. The performance of the microsphere columns is more than 1000 times that of classical LC systems and equals that of open tubular (capillary) GC columns.