Aims/hypothesis. Diabetes is induced by multiple low doses of streptozotocin (MLD-STZ) in male mice of susceptible strains. In this model beta-cell injury and T-cell-mediated inflammatory reactions are induced. Probably, reactive oxygen species (ROS) participate in the destruction of beta cells. The effects of ROS can be counterbalanced by several antioxidant systems. One of these is metallothionein (MT), cytosolic proteins that are induced by zinc ions (Zn²⁺) and scavenge hydroxyl radicals (^·OH). The effect of Zn²⁺ on MLD-STZ-diabetes was studied. Methods. We gave C57BL/6 and (C57BL/6 × SJL)F₁ hybrid mice either MLD-STZ or in addition Zn²⁺-enriched drinking water. We analysed metallothionein ex vivo in pancreatic islets for protein and mRNA concentration for the isoforms 1 and 2. Pancreatic sections were examined by immunohistochemistry for metallothionein and histologically for insulitis. Results. In both strains, Zn²⁺-enriched drinking water significantly up-regulated metallothionein and prevented MLD-STZ-diabetes and loss of beta-cell function. In the F₁ hybrid mice a variant of MLD-STZ-diabetes was observed. These mice developed hyperglycaemia 10 weeks after the first injection of STZ (in contrast to 2 weeks observed in other mouse strains) and pronounced insulitis. The mRNA of the metallothionein isoforms 1 and 2 were constitutively expressed and slightly up-regulated by Zn²⁺-enriched drinking water. All islets cells stained for metallothionein. Conclusions/interpretations. Drinking water enriched with Zn²⁺ significantly up-regulated metallothionein production in pancreatic islets of mice and prevented diabetes induced with MLD-STZ. [Diabetologia (2000) 43: 1020–1030]