Previous reports have described a syndrome of paresthesias, weakness, seizures and hypophosphatemia in patients and animals receiving intravenous hyperalimentation. In this report we describe a group of five patients who developed this syndrome while on oral caloric intake and three patients who received only modest amounts of hyperalimentation therapy. As an experimental corollary, studies were performed in starved and normal dogs with calories infused via an intragastric catheter. The serum inorganic phosphorus (Pi) fell slightly in normal animals from 4.8-2.5 mg. %. In the starved dogs with diarrhea or vomiting the Pi fell gradually from 4.8-1.6. In starved dogs without gastrointestinal symptoms the Pi fell precipitously from 3.7-1.4 mg % on the first day of infusion and remained at that level. Approximately 50% of the starved animals developed the neurological syndrome; none of the normal animals had neurological symptoms.