Objective: To evaluate the association between chromatin structure and sperm motility. Design: Cross-sectional prospective study. Setting: Scanian Andrology Centre, Malmo, Sweden; ENEA Casaccia, Rome, Italy; and Department of Occupational Medicine, Aarhus University, Aarhus, Denmark. Patient(s): One hundred seventy-one males from Danish first pregnancy planner couples (group 1) and 278 Swedish military conscripts (group 2). Main Outcome Measure(s): Sperm chromatin structure assay (SCSA) parameters, DNA fragmentation index (DFI), high DNA stainable (HDS), and sperm motility, which was evaluated manually and by use of computer-aided sperm analysis (CASA). Result(s): A statistically significant negative correlation between DFI and the CASA percentage of motile sperms (group 1: r = -0.53; group 2: r = -0.38) was found. For the manual motility assessment, the correlation coefficients were slightly lower. Furthermore, HDS correlated negatively with CASA sperm motility (group 1: r = -0.39; group 2: r = -0.36) and percentage of World Health Organization category A motile sperm. In multiple linear regression analysis, concentration and SCSA parameters, but not the time of abstinence, were statistically significant predictors of sperm motility. Conclusion(s): There is a moderate correlation between sperm motility and SCSA parameters. The study supports the assumption that both SCSA and motility can be relatively independent predictors of male fertility. (C) 2003 by American Society for Reproductive Medicine.