High-pressure vapor-liquid equilibria of ethane + orange peel oil was determined experimentally by a synthetic method. No liquid-liquid immiscibility was observed in this system. Bubble and dew points were measured at ethane mass fractions ranging from 0.1 to 0.9988 and within temperature and pressure ranges of 282-363 K and 1-10 MPa, respectively. Critical points were also determined experimentally for ethane mass fractions of 0.75-0.9988. At very high ethane concentrations, the experimental results showed double retrograde vaporization behavior, in which the dew point curve has a double-domed shape. In this limited region, increasing the pressure at fixed concentration results in triple- or quadruple-valued dew points. The bubble and dew point data of this work were also compared with those of ethane + lemon peel oil and ethane + limonene, indicating an almost perfect match between all three systems. Even the double retrograde behavior of the orange oil system showed good agreement with that of ethane + limonene, even though the oil is composed of numerous components. The experimental data were correlated with the Stryjek-Vera modified version of the Peng-Robinson equation of state using the Mathias-Klotz-Prausnitz mixing rule with two binary interaction parameters. The results showed fairly good agreement with the data. (C) 2003 Elsevier B.V. All rights reserved.