The concept of using pharmacokinetics for prophylactic dose tailoring with limited blood sampling in clinical practice has been demonstrated for factor VIII but not for factor IX. The pharmacokinetics of factor IX are more complicated than for factor VIII and also differ between plasma-derived and recombinant factor IX. Therefore, the pharmacokinetics of factor IX need to be further explored in clinical trials including comparative studies of prophylaxis with different factor IX concentrates. These are the main conclusions drawn from two of the last manuscripts written by Professor Sven Björkman and published in Haemophilia. Professor Björkman suddenly and unexpectedly died last summer. Thanks to the academic network created around his skill and through his enthusiasm for the pharmacokinetics of clotting factors and ability to convey his wisdom to others, this work will continue. Sven Björkman opened a new era in hemophilia prophylaxis.