Inglehart applies a four item ranking scale to measure post-materialism which is used for cross-cultural and cross-temporal comparative purposes. The aim of this research is to test measurement invariance of the scale to establish to what extent the scale produces comparable results in time and between countries. We use Eurobarometer data to test longitudinal comparability for ten countries (France, Belgium, the Netherlands, Italy, West-Germany, Luxembourg, Denmark, Ireland, Great Britain and North Ireland) over a period of 20 years (1976-1997). With the exception of Denmark the within-country longitudinal comparisons indicate that measurement invariance is a tenable assumption. However, the findings of the cross-cultural analyses indicate that the meaning assigned to the four items differs slightly between countries, indicating a lack of comparability of the average level of post-materialism between countries. Findings also suggest that a lack of unidimensionality of the scale might cause this incomparability.