Nitric oxide (NO) has been implicated centrally as an inhibitory neuromodulator, acting in short feedback loops. Neurons capable of NO synthesis have been localized in various thirst-related hypothalamic nuclei. Intracerebroventricular (icv) injection of L-arginine (L-arg), the precursor for NO, has previously been shown to attenuate both dehydration- and angiotensin II (Ang II)-induced drinking behavior. The present study further examines the effects of L-arg on drinking. We confirmed that icv administration of L-arg (50 microg) reduced water intakes induced by both 24 h water deprivation and icv Ang II (250 ng). We additionally showed that L-arg inhibited the water intake induced by peripheral injection of Ang II and the intake of 0.3 M NaCl following 24 h sodium depletion. We demonstrated the behavioral specificity of L-arg treatment by showing that it did not inhibit the intake of sucrose in food deprived rats and did not act as an unconditional stimulus for the formation of a conditioned taste aversion. These results lend further support to the idea that NO plays a role in modulating fluid balance and drinking behavior.