Cases of chronic copper intoxication of infants via the ingestion of water, as investigated recently in certain regions of Bavaria and the EMs district, have been prompting a quest for additional risk factors which enhance the effect of copper, even though they do limit its frequency rate. The water from water wells, which had been incriminated, was never of a quality standard that would classify it as "drinking water", i.e. as potable water, so that one must consider not only physiological/biochemical but also water-conditioned/chemical causes. Copper alone as the sole risk factor--and in the concentrations considered to be suspect so far--will not suffice to explain the number of cases recorded to date. Basing on the established knowledge in toxicology and essentially of copper we arrive at the following points of attack for further research on the causes: Special kinds of copper ingestion of a chemical nature; unusual reaction of the intestinal mucosa to copper; development-conditioned variable coeruloplasmin synthesis or elimination of copper via the bile; delayed degradation of metallothioneine. Until the causes have been definitely clarified, we believe that suitable prophylactic measures should be taken in accordance with the short communication by Eife and Müller-Höcker (Dt. Arztebl. 85 (1988) 11: A 693) or the press release by the Federal Public Health Service dated 18 March 1988.