This Special Issue of ASME Journal of Heat Transfer on Heat Pipe Science and Technology collects papers in the field of two-phase passive systems for thermal management. The modern field of thermal management has evolved and expanded from classical heat and mass transfer and thermofluids.

Thermal management concerns experimental, numerical analysis, and modeling of physical phenomena and technologies for controlling heating and cooling, and specifically this issue deals with the systems, where a phase change occurs together with a fluid transport, without using active devices, such as pumps or compressors.

Most of the papers have been selected at the Joint 19th International Heat Pipe Conference and 13th International Heat Pipe Symposium, held in Pisa from June 10 to 14, 2018.

This special issue offers to the reader the flavor of the most important trends in heat pipe studies in the last two years.

The papers have been properly reviewed following the standard Journal procedures.