Biosimilars are more affordable copycat versions of originator biological products in much the same way as generics are copies of small molecule pharmaceuticals. However, while generics are approved on the basis of structural and pharmacokinetic equivalence, the intricate structure of biological medicinal products and the complex nature of their manufacturing process in living organisms impose a separate, and more stringent, regulatory approval process. The aims of this article are (a) to discuss key aspects of the development process and authorization requirements for biosimilars in Europe using published comparative physicochemical and clinical data for EU-approved recombinant human granulocyte colony stimulating factor (rhG-CSF) biosimilars, the most recent addition to the therapeutic category of hematopoietic growth factors, and (b) to demonstrate that the rigorous scientific evaluation process is designed to ensure that their clinical safety and efficacy is not compromised by the abbreviated development program.