The role of nitric oxide (NO) in paraquat (PQ)-induced neurotoxicity is still not fully understood. In this study we used N(G)-nitro-L-arginine methyl ester (L-NAME), a non-selective nitric oxide synthase (NOS) inhibitor, in order to examine the effects of NO, reactive oxygen species (ROS) generation and lipid peroxidation (LPO) development during PQ-mediated neurotoxicity. Oxidative stress development in the striatum of Wistar rats intrastriatally (i.s.) poisoned with PQ (and in some cases pre-treated with L-NAME) was investigated by measuring superoxide anion (O(2)(.)?), malondialdehyde (MDA) and nitrate (NO(3)?), 30 min, 24 hours and 7 days after treatment. L-NAME pre-treatment provided the possibility to distinguish the role of ROS from reactive nitrogen species (RNS) in oxidative stress development induced by PQ. Our results confirm the involvement of NO in PQ-mediated neurotoxicity and reduced LPO by L-NAME pre-treatment implying that the latter has a protective role.