The 4th International Conference on Ad-Hoc Networks and Wireless (ADHOC- NOW 2005)was held October 6 8,2005in Cancun, Mexico. Adhoc Now started as a workshop in 2002 and was held at the Fields Institute in Toronto. In 2003, it was held in Montreal, and in 2004 it was held in Vancouver. 2005 was the ?rst yearfortheconferencetomoveoutsideofCanada.Thepurposeoftheconference is to create a collaborative forum between mathematicians, computer scientists, and engineers for research in the ?eld of mobile ad hoc and sensor networks. In 2005, we received over 100 submissions from 22 di?erent countries:...