The surface segregation of In and S from a dilute Cu(In,S) ternary alloy were measured using Auger electron spectroscopy coupled with a linear programmed heater. The alloy was linearly heated and cooled at constant rates. Segregation data of a linear heat run showed surface segregation of In that reached a maximum surface coverage of 25% followed by S, which reached a coverage of 30%. It was found that after In had reached a maximum surface coverage, it started to desegregate as soon as the S enriched the surface until In was completely replaced by S. The segregation parameters, namely, the pre-exponential factor (D0), activation energy (Q), segregation energy (ΔG˚) and interaction energy (Ω) were extracted from the measured segregation data for both In and S segregation in Cu by simulating the measured segregation data with a theoretical segregation model (modified Darken model). The segregation parameters obtained for In segregation in Cu are D0 = 1.8 ± 0.5 × 10−5 m2 s−1, Q = 184.3 ± 1.0 kJ.mol−1, ΔG˚ = −61.4 ± 1.4 kJ.mol-1, ΩCu−In = 3.0 ± 0.4 kJ.mol−1; for S segregation in Cu the parameters are D0 = 8.9 ± 0.5 × 10−3 m2 s−1, Q = 212.8 ± 3.0 kJ.mol−1, ΔG˚ = −120.0 ± 3.5 kJ.mol−1, ΩCu−S = 23.0 ± 2.0 kJ mol−1 and the In and S interaction parameter is ΩIn−S = −4.0 ± 0.5 kJ.mol−1. The initial parameters used for the Darken calculations were extracted from fits performed with the Fick's and Guttmann model. Copyright © 2013 John Wiley & Sons, Ltd.