The retention behaviour of polynuclear aromatic hydrocarbons on packed columns, with supercritical 1,1,1,2-tetrafluoroethane (KLEA) as the mobile phase, has been investigated. The variation of density of KLEA with pressure was calculated from the Martin-Hou equation of state, end comparisons made of k＇ for the polycyclic aromatic hydrocarbons (PAHs) in isopyknic KLEA and CO2. There is little evidence of specific interactions of KLEA with PAHs, although the molecular weight range of supercritical fluid chromatography (SFC) for PAHs should be extended.