Metallothioneins are low molecular weight, cysteine-rich, heavy-metal binding proteins. They are present in some Prokaryota, fungi, plants and animals. Attempts to isolate native plant proteins failed but many metallothionein genes were identified in mono- and dicotyledons and also in some gymno- sperms and algae. They are organised in small gene families, like in animals genomes and their expression is upregulated by different endo- and exogenous factors, including metal ions. In contrast to animal metallothionein genes, they don’t form clusters, but they are distributed through plant genomes. Further- more expression most of them is organspecific. It was suggested that plant metallothioneins may be involved in essential metal ion homeostasis and metal ion detoxification, they could also protect tissues against oxidative stress.