A condition for representativeness of island tidal measurements is found on the assumption that disturbances in the tidal field due to interaction of a tidal wave and a compact set of islands (an archipelago) must be small compared with undisturbed tidal elevations. The corresponding condition for a single island follows from the above as a particular case. It is shown that tidal characteristics belonging even to small islands may be nonrepresentative from the point of view of possibility of their spreading onto the deep ocean. This takes place specifically for islands situated within nodal zones and in the vicinity of amphidromic centers. ¿ American Geophysical Union 1995