The roles of the 37 species in the family Canidae (the dog family), are of great current interest. The Gray Wolf is the largest canid and their roles in food webs are much researched, as are those of Domestic Dogs, Coyotes and Red Foxes. Much less is known about the other canid species and their ecological roles. Here we describe general food web theory and the potential application of network theory to it; summarise the possible roles of predators in foodwebs; document the occurrence, diet and presumed functions that canids play in food webs throughout the world; give case studies of four threatened canid species of top, middle and basal trophic positions and six anthropogenically affected species; and identify knowledge limitations and propose research frameworks necessary to establish the roles of canids in food webs. Canids can be top-down drivers of systems or responsive to the availability of resources including suitable prey. They can be affected anthropogenically by habitat change, lethal control and changes to basic resource availability. They can be sustainable yield harvesters of their indigenous prey or passengers in complex ecosystems, and some are prey of larger canids and of other predators. Nevertheless, the roles of most canids are generally poorly studied and described, and some, e.g. GrayWolves, Coyotes and Australian dingoes, are controversial. We advocate mensurative and experimental research into communities and ecosystems containing canids for a quantitative understanding of their roles in foodwebs and consequent development of bettermanagement strategies for ecosystems.