Comparison of radiation-induced segregation (RIS) measurements from austenitic iron- and nickel-base alloys with calculations using the Perks vacancy-driven RIS model have shown that chromium segregates slower and iron segregates faster than expected from high temperature diffusion measurements. The effect is more pronounced in nickel-base alloys. The segregation process is affected by short range ordering forces and the ordering is strongest in nickel-base alloys. Since nickel enriches and chromium depletes in all iron-chromium-nickel alloys under irradiation, a tendency to form nickel- chromium pairs reduces the chromium segregation, especially in nickel-base alloys. In this work, Perks' model is altered to include ordering energies, and the calculated RIS is compared to segregation measurements from iron-chromium-nickel alloys irradiated with 3.2MeV protons. A single set of ordering energies, an attractive potential between nickel and chromium and a repulsive potential between nickel and iron are used for each alloy. Calculations that do not include ordering overpredict the chromium depletion by up to 4 at% in iron-base alloys and 8 at% in nickel-base alloys. Calculations that include the ordering reduce the difference between model predicted and measured chromium concentrations to less than 2 at% for most iron- and nickel-base alloys.