The crystalline content in high pressure compacted polymeric powders has been investigated as a function of moulding pressure. It has been noted that the crystallinity C_p varied with the pressure as [C₀ — βP^α] where α and β were material dependent constants. There also appears a correlation between α, β, and an empirically defined factor which is related to the glass transition temperature, melting point, and compressive yield strength for all the polymers studied. The results have been discussed in terms of various processes taking place during the high pressure compacting step.