The respiratory syncytial virus (RSV) fusion (F) protein is synthesized as an inactive precursor (F0), which subsequently undergoes post-translational cleavage to give the disulphide bond-linked F1 and F2 subunits. The methodology detailing the use of two-dimensional electrophoresis, endoglycosidases, and alpha-mannosidase inhibitors, as applied to investigating F protein glycan maturation, is given. Examples are used to show how this methodology was used to provide evidence for glycan heterogeneity within the mature F protein.