What features of the mustelids might yield insight into issues of general importance for conservation and ecology? This review focuses attention on correlates of threat, intra-guild competition and reintroductions. Using the IUCN classification of the status of mustelid species, I constructed a statistical model of correlates of threat. This suggested that otters and martens, and mustelids with small distributional range sizes, were the most threatened. Whether or not a species was hunted and its habitat specificity did not correlate with threat. This analysis should be treated as indicative only, because the response variable (threat) was not totally independent of the explanatory variables. There is growing evidence that intra-guild predation influences mustelids. In Scotland, there is some evidence for spatial segregation between Pine Martens and Red Foxes (a potential predator). Pine Marten relative abundance was higher in woodland interior than woodland edge. Red Foxes were equally abundant in woodland edge and interior. However, habitat fragmentation (woodland patch size) was the strongest correlate of relative abundance of both species. Research on mustelids has demonstrated the importance of appropriate release techniques during reintroductions. It has also shown that reintroductions of small numbers of animals can be successful, provided that they are conducted in high quality habitats. The implication is that habitat suitability assessments need to be given high priority. In this respect, research in Britain suggests that inferring habitat needs from areas of relict distribution may lead to highly misleading conclusions.