A measurement of strange baryon and antibaryon production in Pb-Pb collisions has been carried out by the NA57 experiment at the CERN SPS, with 40 and 158 A GeV/c beam momentum. Results on Lambda, Xi and Omega hyperon yields at mid-rapidity in the most central 53% of Pb-Pb collisions at 40 A GeV/c are presented and compared with those obtained at higher energy, in the same collision centrality range. The Lambda and Xi(-) yields per unit rapidity stay roughly constant while those of Omega(-), A, (&UXi;) over bar (+) and (&UOmega;) over bar (+) increase when going to the higher SPS energy. Hyperon yields at the SPS are compared with those from the STAR experiment in root(s)NN = 130 GeV Au-Au collisions at RHIC. (C) 2004 Elsevier B.V. All rights reserved.