An enzyme electrode for the specific determination of omega-3 and omega-6 fatty acids from the mixture of essential fatty acids (EFAs) was developed by using lipoxygenase (LOX) (EC 184.108.40.206) from soy beans in combination with a dissolved oxygen (DO) probe. The enzyme electrode showed different sensitivities for linoleic (LA) and a-linolenic acids (ALA), the most common essential fatty acids. Enzyme electrode response depends linearly on LA concentration between 12.8-160.5 muM and ALA concentration between 3.8-18.9 muM in borate buffer, 0.2 M at pH 9.0. However, in phosphate buffer 0.2 M at pH 6.0 linearity is in the range of 7.5-22.5 muM of ALA concentration at 5 minutes response times. Moreover, maximum electrode response was found in borate buffer at pH 9.0 and 30 C.