The effect of inhaled epichlorohydrin (E) on rat sperm motility characteristics was evaluated. Male F-344 rats were exposed to 100ppm E via inhalation for 4 hrs on the morning of d 0 and killed immediately and on d 1, 2, 6 and 14 postexposure. Videotapes of cauda epididymal sperm were analyzed (300-350 sperm/sample) with a Hamilton Thorn Motility Analyzer. E did not affect the percentage of motile sperm at any time. However, transient changes in sperm velocity were found. On d 1 postexposure mean progressive (straight-line) and mean path (smoothed curvilinear) velocity were significantly decreased to 80% and 85% of control, respectively. The progressive velocities of sperm from both control and treated rats were normally distributed, indicating a general effect of E on all sperm as opposed to a more severe effect on a specific sperm subpopulation. Both velocities remained slightly but significantly decreased on d 2 (92% and 93% of control for progressive and path velocity, respectively), and were unaffected at later timepoints. Other endpoints (testis and epididymis weights, testicular spermatid counts and cauda epididymal sperm reserves) were unaltered by E. Thus, inhaled E produced specific, transient decreases in rat sperm velocity. (Copyright (c) 1990 by the Society of Toxicology.)