Determination of paraffins (P) and naphthenes (N) by the 13X molecular-sieves method has to be preceded by a separation of PN from A. If one wants to perform the latter separation by gas chromatography, one is faced with the usually underestimated problem of boiling-point separation counteracting type separation. It is shown that for naphthas with a ucp of up to 200°C, complete PN-from-A separation can only be realized by two-stage fractionation. The polar and non-polar columns required for this procedure have been integrated with a 13 X column to constitute a PNA analyser which yields quantitative P, N and A information for every carbon number through C11. As a result of both the essentially complete type separation and the fully automatic operation, the analytical data show a high degree of repeatability as well as reproducibility. A module matching the analyser allows additional differentiation between 5- and 6-ring naphthenes as well as n- and isoparaffins. The PONA analysis of olefinic naphthas is still under investigation. A few suggestions are given for additional analytical problems that may be handled by this analyser. The analyser will be made commercially available.