This group of tapeworms are usually medium to long (1 m to 10 m) parasites of all groups of vertebrates. It is a diverse group, and many species are of medical importance.
Eggs deposited in water hatch to release a coracidium, which is eaten by a crustacean first intermediate host and develops into a procercoid. If the procercoid is eaten by a suitable second intermediate host (aquatic vertebrate) it develops into a plerocercoid, and that develops into an adult if eaten by a suitable definitive host.
The scolex possesses bothria and may also have hooks. The strobila is segmented. The uterus usually has a median genital pore, and the proglottids often mature in synchrony along most of the length of the tapeworm. There is a uterine pore through which eggs are released, although gravid proglottids may also detach.