['To assess the effects of progesterone and acetyl-L-carnitine used before semen cryopreservation-thawing on sperm motility parameters and plasma membrane integrity.', 'Prospective cohort study.', 'Academic tertiary center.', 'Subfertile men undergoing semen evaluation.', 'Before cryopreservation, spermatozoa were incubated with water-soluble progesterone (1 and 10 microM), acetyl-L-carnitine (2.5, 5, 10, and 20 mM), or both (progesterone, 1 microM; and acetyl-L-carnitine, 5 mM).', 'Postthaw change of motility parameters (computer-assisted measurements) and vitality-membrane integrity (examined with eosin-Y staining and annexin V-Cy3 binding assay).', 'There were no statistically significant differences between control samples and samples treated with progesterone and/or acetyl-L-carnitine for cryosurvival rate, motility parameters, or membrane integrity. The percentages of postthaw cells identified as live showed significantly different results with use of the eosin-Y staining and annexin V binding assay.'] Does semen treatment with progesterone and/or acetyl-L-carnitine improve sperm motility or membrane damage after cryopreservation-thawing?