We report our recent work on nonlinear waves, especially in association with

parity-time-symmetric nonlinear optics and rogue waves. The concept of parity-time (PT) symmetry originates from quantum mechanics, where a complex but PT-symmetric potential could still possess all-real spectrum. This concept later spread to optics, where an even refractive index profile together with an odd gain-loss landscape constitutes a PT-symmetric system. In this optical setting, the interplay between PT symmetry and nonlinearity becomes meaningful. Although PT systems are dissipative, they exhibit many properties of conservative systems. In addition, they exhibit some novel properties which have never been seen before. Rogue waves are spontaneous large nonlinear waves which arise from constant backgrounds. They are linked to some extreme wave events in oceanography and optics. Explicit rogue-wave expressions in integrable systems can be derived by advanced techniques. In this talk, we describe novel properties in PT-symmetric nonlinear systems, and demonstrate techniques to derive rogue wave solutions in certain integrable systems.