Temperature modulated differential scanning calorimetry (TMDSC) is used for the first time to measure the wax appearance temperature (WAT) of crude oil samples. The commercial implementation of TMDSC chosen for this study is alternating differential scanning calorimetry (ADSC) marketed by Mettler-Toledo. We show that changes in the ADSC signals exhibit excellent correlations with WATs measured using conventional differential scanning calorimetry, DSC. For oil samples having low wax contents, ADSC is a more sensitive technique for identifying the onset of wax crystallisation and, specifically, the phase angle between the heating rate and heat how modulations is extremely sensitive to this process. (C) 2001 Elsevier Science Ltd. All rights reserved.