Animal and human gametes and embryos must be protected from infection durin
g low temperature storage. In human, the obligatory screening of everyone w
ishing to store tissue and the provision of quarantined storage when this i
s impractical would minimise the risks. Straws are preferred for embryo sto
rage because freezing in plastic vials is detrimental. Aseptically filled s
traws do not leak dye, E. Coli or Newcastle Disease virus and even potentia
lly leaky straws do not contaminate their environment when wrapped in a lay
er of plastic film. Embryo viability was high after freezing in straws cont
ained in a sealed plastic envelope. Storage in the vapour phase of a liquid
nitrogen tank may increase the likelihood of gametes and embryos being dam
aged as a result of accidental warming.