Nitric oxide (NO) is an inorganic free radical, that plays an important role in regulation of variety processes in living organisms. Soils are an important source of NO, produced during denitrifica- tion, nitrification and reduction of NO 3 - to NH 4 +. In plants NO production depends on the activity of nitric oxide synthase and/or nitrate reductase as well as non enzymatic generation of NO can be detected. Similarly as in animals, in plant cells NO is widely regarded as a signaling molecule. There are a number of data proving that different NO donors (sodium nitroprusside, S-nitrosoglutathione, S-nitroso-N-acetyl- D-penicillamine) stimulate seed germination of many plants. Moreover endogenous synthesis of NO during seed germination was reported, indicating its role as a link to activation of embryonic axes. Al- though it is not questionable that NO acts as mediator of seed germination its mode of action in this process is still known only fragmentary. NO stimulates germination of photoblastic seeds, by activation of phytochrome signal transduction pathway. On the other hand NO interact with classical phytohormo- nes (ethylene, abscisic acid, gibberellins) involved in regulation of seed germination.