Wavelength division multiplexing techniques in combination with Erbium-Doped Fiber-Amplifiers will allow for the second “order-of-magnitude” capacity increase for long-haul transmission systems within the past few years. The transmission of many WDM channels over long distances can be limited by a variety of phenomena, including the finite bandwidth of the EDFA repeaters, the nonlinear interactions between channels, and the noise accumulation along the chain of amplifiers. Large transmission capacity enhancements have resulted from an increased understanding of these effects. Important strides have been made in areas of dispersion management, gain equalization, and modulation formats which have made possible the demonstration of large data transmission capacity. This paper describes techniques used to transmit many WDM channels over transoceanic distances. Data is presented for several WDM experiments including the transmission of 320 Gb/s over transoceanic distances using 64 channels of 5 Gb/s.