Instead of blindly tracking the rapid downsizing of supply voltage (V ) in technology scaling, high-/mixed-voltage radio-frequency (RF) and analog CMOS circuits have emerged as a prospective alternative comes of age. An elevated V, or a hybrid use of I/O and core V's, in conjunction with thinand thick-oxide MOS transistors open up many possibilities in defining circuit topologies, while maintaining the speed and area benefits of advanced processes. Circuit reliability can be guaranteed through advanced circuit techniques. This paper aims to provide a glimpse of the basic concept, system design considerations and circuit examples. A wide variety of RF and analog CMOS circuits designed based on such techniques are examined and new topologies are proposed. Those circuit topologies comprise the RF power amplifier, the low-noise amplifier, the mixer, operational-amplifier- based analog circuits, the sample-and-hold amplifier and, finally, the line driver. Reliability considerations such as oxide breakdown, hot carrier injection (HCI), time dependent dielectric breakdown (TDDB), and bias temperature instability (BTI) will be discussed, and their implications in different types of circuits will be justified. The outlined principles are extendable to other RF and analog circuits, motivating the adoption of new voltage-conscious topologies in ultrascaled CMOS processes. © 2010 IEEE.