In this paper the modification of the amine end groups of polyamide-6 (PA-6) granules with diketene and the diketene acetone adduct in supercritical and subcritical CO2 is described. The modified polyamide samples were characterised by end group titrations, viscosity measurements and FTIR spectroscopy. The aim of the modification of the amine end groups of PA-6 was to obtain a polyamide with an amine end group content of around 10 mmol/kg PA-6, which is known to exhibit a satisfactory melt stability. It was expected that the end group modification could be achieved without changing other properties of the polymer, since in supercritical CO2, relatively mild reaction conditions can be applied. Indeed, chain scission can be avoided, but unfortunately, the described modification resulted in coloured PA-6 granules. By comparing the current results with our earlier data on amine end group modification in supercritical CO2 it is learnt that 1,2-epoxybutane is the preferred blocking agent. (C) 2003 Elsevier B.V. All rights reserved.