To evaluate the association between neutral alpha-glucosidase (NAG) activity and sperm DNA fragmentation (DFI), ejaculates from 24 men undergoing evaluation for sperm DNA damage as a part of infertility assessment were analysed. The mean +/- SD and range for the semen quality of the 24 ejaculates are as follows: volume (3.1 +/- 1.3, 1.8-6.0 ml); sperm concentration (45.6 +/- 41.1, 1.3-151.2 x 10(6) ml(-1)); sperm motility (52.8 +/- 28.8, 1-95%); sperm with fragmented DNA (17.6 +/- 15.4, 1.7-56.0%); sperm with immature chromatin (9.6 +/- 3.8, 2.5-19.1%); NAG activity (37.9 +/- 18.3, 4.4-75.3 mU ml(-1)). The only sperm parameter significantly correlated with neutral alpha-glucosidase is the percentage of sperm DFI [correlation coefficient (r) = 0.4376, P = 0.03].