The concept of similar biological medicinal products (‘biosimilar’ medicinal products) allows pharmaceutical companies to develop products based on an abridged dossier once the marketing protection of the ‘reference’ biological medicinal product has expired. A biosimilar medicinal product can be granted a marketing authorization provided that its similarity to a reference product is established in terms of quality, safety and efficacy (step-wise comparability exercise). A decision to launch a biosimilar medicinal product on the market is taken if it has a similar efficacy and comparable or better (less) immunogenicity than the chosen reference biological medicinal product. However, this decision is based on limited data and the comparability program may detect substantial differences in immunogenicity profiles but is likely incapable of detecting rare events. This is why clinical experience, through clinical trials and extensive pharmacovigilance programs, remains the most reliable way to assess the immunogenicity and tolerance profile of recombinant therapeutic proteins. Substitution of one biological medicinal product by a biosimilar medicinal product is not currently recommended before long-term clinical efficacy and safety have been acquired in all relevant populations. Here we review recent regulatory guidelines provided by EMEA and comment on the marketing authorizations and risk management plans of two recently approved biosimilar somatropins.