It is with deep sadness that I write this short obituary of Professor R.A. Vollenweider. I am highly indebted to him for his scientific suggestions, teaching and discussions, but most of all for his friendship, which goes back to 1950. R.A. Vollenweider was born in Zürich (Switzerland) on June 27, 1922. He obtained his PhD degree in Biology from the University of Zürich in 1951, subsequently becoming Research Assistant at the Hydrobiological Institute, Kastanienbaum (Switzerland).