Interest and activity in the equatorial oceans (defined arbitrarily as that part of the oceans within ten degrees of the equator) have undergone a remarkable expansion in the last four years. The previous IUGG report (O'Brien, 1979) listed about one hundred references – the present one lists over two hundred and fifty. Among the many reasons for this growth, a primary one is the realization of the rapid nature of equatorial responses. The vanishing of the Coriolis parameter in the presence of density stratification means that the ocean can respond strongly to basinwide winds on the climatically important, and observationalIy accessible, annual and interannual time scales. This realization has taken hold as the result of an interplay among theory, modelling and observation.