Concentration interest on one detail of a complex problem often results in oblivion of broader aspects and neglect of insights of the past. In the 1970s, hormones are "in" and electrolytes are "out" of the continuing discussions about diabetes mellitus. Preoccupation with dosage and routes of insulin administration in cases of diabetic ketoacidosis has resulted in a large number of publications about this single practical but not fundamental characteristic of the therapy. Quantitative and qualitative specifics of fluid and electrolyte therapy are missing, not only in the majority of these reports, but even in some textbooks. Far from being taken for granted, consideration of phosphate, calcium, magnesium, solute load, thiamine, nitrogen balance, and other issues once in the center of interest now seems to be forgotten, whereas 20 years ago, at the conclusion of nearly four decades of intensive investigation, the pathophysiology of disturbances of body fluids and electrolytes was