Using a questionnaire for data collection and two multivariate techniques for analysis this paper reports on the concepts undergraduate physics students in England hold regarding quantum phenomena. The analysis is by Cluster Analysis to find underlying groups of concepts and Multidimensional Scaling to map the concepts onto a three dimensional space. A sample of 338 first and second year undergraduates, from six institutions, was surveyed during 1998. Cluster Analysis generated three distinct Clusters which are named: Quantum thinking, Intermediate thinking and Mechanistic thinking. Multidimensional Scaling allowed the responses to be mapped onto three dimensions named: Absolute - Vague, Mechanistic - Probabilistic and Locatable - Non-locatable. The results suggest that at the level of the group there is an underlying structure to the students’ responses. Insight into a complex topic has been gained which is in agreement with earlier work with pre-university physics students in England and undergraduate physics students in the USA.