Dehydrins are proteins that accumulate in vegetative tissues subjected to various dehydrating stress conditions such as cold, drought, and salinity and in seeds at later stages of embryogenesis. Here, we report on two highly identical dehydrin genes, DHN1a and DHN1b, in wild and cultivated grapes, Vitis riparia and Vitis vinifera, and their expression in different tissues and under different environmental conditions. The two genes and their transcripts can easily be distinguished by RT-PCR because DHN1b has an 18 bp deletion compared to DHN1a. V. riparia expressed only DHN1a; V. vinifera expressed both DHN1a and DHN1b. Spliced transcripts, DHN1-S, encoding a putative YSK(2)-type dehydrin were present in low amounts in control leaves, but in high amounts in buds and seeds. Unspliced transcripts, DHN1-U, accumulated to high levels in buds and seeds. Cold, drought, and ABA treatment increased accumulation of both DHN1-S and DHN1-U in leaves, whereas short-day treatment increased only DHN1-S. The possible relation of these results with the difference in freezing stress tolerance between V. riparia and V. vinifera is discussed.