The review summarises the contemporary knowledge on occurrence. produc
tion, and estimation of different microbial nitrate reductases (NR). T
he main interest is focused on two basic NR types: dissimilatory and a
ssimilatory NR, both playing an important role in nitrate metabolism o
f bacteria. NR are putatively responsible for the presence of nitrosam
ines in many food items. In the second part, quantitative and qualitat
ive methods of NR estimation are compared.