We present a rare case of a 66-year-old woman with the syndrome of inappropriate antidiuresis (SIAD) accompanied by an empty sella whose symptoms were seen twice in the eight years after the administration of non-steroidal anti-inflammatory drugs (NSAID) or prochlorperazine. No diuresis or suppression of the plasma level of vasopressin (AVP) was observed after water loading upon cessation of the causative agents. Suppression of the renin-aldosterone system and a low plasma level of atrial natriuretic peptide (ANP) were observed during natriuresis. The plasma levels of AVP were increased after water loadings. Restriction of water intake ameliorated the symptoms and reduced hyponatremia. These findings suggest that NSAID or prochlorperazine caused overt SIAD twice in eight years. The water loading test itself stimulated the release of AVP and a suppression of the renin-aldosterone system played a more important role in natriuresis than ANP in this case.