Another explanation of the large difference in the DNA quantities obtained from neat blood swabs is the variation in extraction efficiency among swab types. Although the Puritan FABSwab was ranked highest overall for sampling biological materials and provided the consistently high quantities of DNA mentioned above from neat blood, it did not yield the highest quantity of DNA during tests of its extraction efficiency. This demonstrates that the effect of extraction efficiency, whilst potentially affecting overall swabbing efficacy, may have been outweighed by high collection efficiency. Previous comparison of the DNA collecting capacity of polyester and cotton fabric swatches (10) showed that, whilst there was no significant dif- ference between the DNA quantities collected by cotton and polyester as a whole, the amount of DNA collected was inver- sely proportional to the density of the fibers in the fabric. This finding does not concur with the results of this study, which ranks the FABSwab higher for DNA collection efficiency than other cotton swabs, which appear, by both weight (Table 1) and observation, to be less densely wound. One possible expla- nation for this discrepancy is that woven fabric swatches as used by Mulligan et al. (10) may not be directly comparable to wound swabs due to the differences in the structure of their fibers.