A discrepancy in the magnitude of thujone concentrations in distilled pre-ban absinthe has existed until now. Concentrations of 260 mg L−1 were derived at by theoretical calculations. Tests of authentic pre-ban absinthes and studies concerning absinthes produced according to historic recipes found concentrations below 10 mg L−1. In this study, the behaviour of thujone during distillation was studied and a significant discrimination was determined (80% yield in water-cum-steam distillation). The thujone concentrations in distilled pre-ban absinthe were then calculated with regard to the composition of wormwood derived from a literature review. Due to the large deviations of oil content and thujone concentration of wormwood, a typical Absinthe Suisse de Pontarlier from Duplais' 1855 recipe might have contained between zero and a maximum of 76 mg L−1 of thujone, the average was calculated as 23 mg L−1 with a standard deviation of 21 mg L−1. It was proven that the previous calculations overestimated the thujone content of distilled absinthe and the discrepancy was resolved as our new calculations are in good accord with the experimental findings. Copyright © 2007 Society of Chemical Industry