The World Ocean Circulation Experiment (WOCE) is the most ambitious global oceanographic program ever undertaken. The program combines in situ measurements of unprecedented quality and coverage with state-of-the-art satellite observations and modeling. The Indian Ocean expedition is one part of the WOCE field endeavor, with other expeditions covering the Pacific, Atlantic, and Southern Oceans. Focusing on 1995, the Indian Ocean was intensively sampled by the international oceanographic community using a fleet of oceanographic research vessels and relying on the cooperation and resources of many countries (Figure 1). In technique and scope the expedition far surpasses the last great coordinated Indian Ocean effort, the International Indian Ocean Expedition of the 1960s [Wyrtki, 1971].