The concept of an ecological footprint is intriguing and has prompted an avalanche of theoretical and applied research. In recent publications both the scientific basis and the policy relevance of this concept have been given ample attention, while also much empirical work has been undertaken to assess the value of the ecological footprint in different regions or countries of the world. The paper starts with a concise critical overview of the current discussion on ecological footprints. Its main aim, however, is to provide a meta-analytic assessment and interpretation of the various empirical findings in the recent literature that offer estimated values or ranges of the ecological footprint indicator. The sensitivity of ecological footprints for the stringent assumptions made in the calculation schemes is investigated using frequency analyses, cross-tabulation methods and decision-tree induction methods (a recent technique based on pattern recognition methods). The results show that methodological choice, geographical scales and year of data collection offer a significant explanation for variations in results. The paper concludes with some suggestions for further research. © 2004 Regional Studies Association.