Am-in, N., Kirkwood, R. N., Techakumphu, M. and Tantasuparuk, W. 2010. Effect of storage for 24 h at 18 degrees C on sperm quality and a comparison of two assays for sperm membrane lipid peroxidation. Can. J. Anim. Sci. 90: 389-392. Boars having normal (71.1 +/- 1.2%; n = 10) or low (35.12 +/- 3.9%; n = 10) sperm motility 24 h after collection were used, and semen was evaluated following storage in Beltsville Thawing Solution (BTS) for 24 h at 18 degrees C. Sperm lipids were extracted and lipid peroxidation quantified. No differences were evident in fresh semen, but after 24 h, sperm motility, viability and membrane permeability in the low motility group were lower (P <0.001) compared with the normal motility group. Sperm membrane lipid peroxidation was greater (P <0.001) in the low motility group. A factor influencing sperm storability is membrane lipid peroxidation, which can be accurately assayed using a commercial kit.