Supercritical fluid extraction is an interesting alternative for the fractionation of essential oils, in order to obtain concentrates or compounds of interest. This technique requires information about the distribution of the components of the mixture between the phases present at different conditions of pressure, temperature and composition. In this work equilibrium information of three bioactive essential oils (Salvia officinalis, Mentha piperita and Tagetes minuta oil) with near-critical and supercritical carbon dioxide is measured using a dynamic apparatus in the range of 313-323 K and 60-120 bar. The distribution of monoterpenes, oxygenated terpenes and sesquiterpenes in the extract phase is determined by gas chromatography in order to explore the best operating conditions for the separation of the fractions or compounds with higher biocidal activity. Predictive calculations are performed using the group contribution equation of state (GC-EOS) and compared with the experimental data. (C) 2011 Elsevier B.V. All rights reserved.