1 INTRODUCTION  
2 DESCRIPTION OF THE DATA  
2.1 Sample Selection  
2.2 Environment Definition  
2.3 Galaxy Size Determination  
3 OBSERVED MASS–SIZE RELATIONS  
3.1 Mass–Size Relation for Morphologically-Selected Samples  
3.2 Mass–Size Relation for Colour-Selected Samples  
3.3 The Effect of the Cluster and Galaxy Masses  
4 CONCLUSIONS