We develop a complete linear theory for the effects of islands on low frequency waves of the kind thought to be important in the seasonal and interannual variations of the Equatorial ocean circulation. For an island whose meridional extent is small compared to R, the Equatorial radius of deformation, the waves pass the island almost undisturbed : the current incident on the island flow around it to the north and south and continue downstream in the lee of the island. For islands comparable to or greater in extent than R the mass fluxincident on the island is largely reflected in a manner similar to the case of a meridionally infinite barrier. An incident Equatorial Kelvin wave is reflected as long Rossby waves; symetric long Rossby waves are reflected as Equatorial Kelvin waves while antisymetric ones stop at the island barrier. In allcases a boundary current composed a short Rossby waves forms at the Eastern side of the island and accomplishes the required meridional redistribution of the zonal mass flux. Calculations carried out for the major mid-ocean low latitude islands (The Gilberts and Galapagos in the Pacific; Sao Tome in the Atlantic; the Maldives in the Indian Ocean) show that the propagation of long waves will not be significantly affected by any of these islands and that smallperturbations occur only in their immediate vicinity. (Résumé d'auteur
