Most wireless devices manufactured today are equipped with a plurality of sensors and communication capabilities. Handheld devices can nowadays connect through multiple communication networks, such as 3G/LTE, WiFi, Bluetooth, Zigbee, WiMax, UWB, etc. They are also capable of sensing the environment, taking still images or videos, finding their location, detecting hand movements via accelerometers, and reading RFID tags. These devices have advanced operating systems capable of sophisticated signal processing and wireless communications. Much research is needed to use the sensing and communication capabilities of the newest generation of wireless devices to build new applications such as real-time youtube or wikis that collect, process, and report live data to public for security, news, or entertainment purposes. Among the applications envisioned for the new technology are vehicular networks, assistive technologies, eHoming (smart home), and the entertainment industry. The powerful capabilities of new smart phones and PDAs motivate new directions in academic research that seek to fully harvest the potential of advanced features for the creation of new network services. Most such emerging services will need the user location, which is not usually trivial to obtain. Interesting applications where location is an important factor for service enabling are assistive technologies, especially for navigation of visually impaired, vehicular safety enhancement, event and situation-aware services, and so on. Despite much effort in recent years on location estimation both using active and passive methods, location estimation remains to be a challenging problem, especially in indoor environments where GPS signal is not available or the GPS location estimate is fairly inaccurate. This special issue tries to address some of the challenges in the location estimation and offer solutions where available. The annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) is one of the premier conferences in the wireless research arena and has a long history of bringing together academia, industry and regulatory bodies. Today, it has become one of the IEEE Communication Society’s flagship conferences in telecommunications. The 22nd IEEE PIMRC was held successfully in Toronto, Canada, from September 11 to 14, 2011, where over 600 researchers met to share their latest research results in wireless technologies. In this special issue, we have compiled the extended versions of the best papers on localization from this conference as well as a few invited papers from well-known experts in this field. The invited authors have done an excellent job in substantially extending the conference version of the papers, which significantly improved the quality of the manuscripts. The objective of this special issue is to provide the readers a timely perspective on the exciting new developments in the field of wireless localization technologies. The first paper, ‘‘A Comprehensive Tutorial on Localization: Algorithms and Performance Analysis Tools’’ by Davide Macagnano, Giuseppe Destino, and Giuseppe Abreu, was originally presented at PIMRC 2011 as a tutorial. The authors diligently converted the half-day tutorial presentation into a long tutorial article to provide a comprehensive view of technological solutions and theoretical fundamentals of localization and tracking (LT) systems for wireless S. Valaee Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON, Canada e-mail: valaee@comm.utoronto.ca