Abstract The smart grid infrastructure requires a widespread management and control system that is based on real time measurements and monitoring processes. The improvements of measurement technologies have facilitated smart metering interfaces by integration of information and communication technologies (ICTs) to field devices. The generation and transmission system operators require measurement and monitoring applications to ensure reliability and flexibility of smart grid while distribution system operators need monitoring for planning demand side management and demand response programs. This chapter deals with smart metering technologies and recent developments in the context of automated meter reading (AMR) and especially advanced metering interface (AMI). The smart meters are introduced in detail with their hardware and communication interfaces. The protocols, standards and security issues of AMI systems are presented in this chapter in addition to phasor measurement unit (PMU) applications. The smart monitoring systems have been introduced in terms of components and architectures in the following sections of this chapter.