The current guidance on similar medicinal products containing recombinant granulocyte-colony stimulating factor (G-CSF) provides recommendations for the non-clinical and clinical development of recombinant G-CSF claimed to be similar to a reference product already authorised in the European Union (EU). This guideline was one of the first product-class specific biosimilarity guidelines and came into effect in February 2006. Since then, several biosimilar filgrastims have been licensed in the EU. It is proposed that the guideline should be updated based on the experience gained with marketing-authorisation applications and scientific advices on biosimilar filgrastims.