Since the late 1970s research has suggested that marsupial spermatozoa did not suffer cold shock. We have re-examined cold shock to investigate problems with freezing of spermatozoa from a dasyurid marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata). Epididymal spermatozoa were rapidly cooled to 0.5 degrees C in a pre-cooled tube held in an iced-water slurry. Upon re-warming all spermatozoa were immotile and the addition of 10% or 20% egg yolk to the sperm medium had no beneficial effect. Spermatozoa that were rapidly cooled to 4 degrees C maintained only 2% motility when re-warmed but the addition of at least 10% egg yolk was beneficial and upon re-warming greater than 65% of the initial motility was maintained. In order to achieve motile spermatozoa at 0 degrees C, controlled-rate cooling at 0.5 degrees C min(-1) was examined. In the absence of egg yolk there was a significant decline in the percentage of motile spermatozoa below 4 degrees C. However, the inclusion of at least 10% egg yolk resulted in no loss of motility in spermatozoa cooled to 0 degrees C. This is the first experimental study indicating that spermatozoa from a marsupial are highly susceptible to cold shock and that the impact of rapid chilling can be mitigated by the addition of 10% egg yolk. The ability to successfully cool the spermatozoa of S. crassicaudata to 0 degrees C may have an important role in future studies examining dasyurid sperm cryopreservation.