The 2018 IEEE IUS SA-VFI challenge consist on estimating blood flow velocities from both simulated and measured ultrasound RF element data sets. The challenge results are meant to be presented during the next IEEE International Ultrasonics Symposium 2018 in Kobe (Japan). The data sets for the challenge consist on pre-beamformed RF element signals using a pre-selected synthetic aperture (SA) sequence on flow phantoms, both simulations and experiments. The details of the provided data sets and example code is given in the main document "2018_IEEE_IUS_SA-VFI_Challenge.pdf". A website for the participants with additional information is available at https://www.creatis.insa-lyon.fr/Challenge/IEEE_IUS_2018/.