Monitoring and control systems that are based on networked wireless sensors have been recognized as an indivisible component for current and future smart systems in many applications such as healthcare, home security, disaster response, and environmental monitoring. From the viewpoint of researchers, developers and even consumers, reliability analysis is an indispensable step before wireless sensor network systems can be widely deployed for mission-critical applications. In this talk, reliability modeling and analysis for wireless sensor networks will be discussed under two different communication paradigms: infrastructure communication and application communication. Five data delivery models (sink unicast, sink anycast, sink multicast, sink manycast, and sink broadcast) will be presented for the infrastructure communication reliability analysis. Impact of different routing algorithms and network topology characteristics like connectivity, average path length, average degree, diameter, and clustering coefficient on the network reliability will also be discussed.