I would think 100% Whey is exactly that. ON 100% Whey ingredient list:
QuadPlex Protein Blend (Ultrafiltered Whey Protein Concentrate, Cross Flow Microfiltration Whey Protein Isolate, Ion Exchange Whey Protein Isolate [All Three Sources Contain Concentrations of Lactoglobulin, alpha-Lactalbumen, Bovine Serum Albumen, Immunoglbulins, Glycomacropeptides, Lactoferrin, Lactoperoxidase, Glycomacropeptides, Lactoferrin, Lactoperoxidase, other closely related Protein Molecules and Glutamine Peptides], Low Molecular Weight and Partially Hydrolyzed Whey Peptides), Artificial Flavor, Acesulfame Potassium, FD and C Red #40.
So, it's not 100% Whey, but probably very close, 95% maybe?