The infrastructure for NEPTUNE consists of five systems: communications, power distribution, system control, time distribution, and data management and archiving. Each of these components must be designed as end-to-end systems, and must be highly fault tolerant. Physical packaging of the seafloor nodes must be accomplished in a way which facilitates science as well as maintenance. The system engineering for NEPTUNE is presently underway, and the approach which is being taken in each area will be briefly described.