Nitric oxide (NO) is one of dozens of lipophilic small molecules that is synthesized from amino acid L-Arginine, O2 and NADPH by nitric oxide synthase (NOS). There is increasing evidence that NO is an important molecular messenger involved in a wide variety of biological processes in different systems. One of the isoforms of NOS enzyme called inducible NOS (iNOS) is stimulated by different stimuli such as lipopolysaccharide (LPS), which is part of the membrane of gram-negative bacteria, which ultimately leads to NO production in the long time. LPS mediated more events for infection. Since NO in biological system is important, in the present study, the effects of LPS on NO production in inbred Balb/c mice via this pathway were examined. The immunological pattern of bacterial LPS as inducer of the immune system in Balb/c mice via NO pathway was investigated. In this study, the bacterial LPS of Salmonella abortus was injected to Balb/c mice among the test group; the control group was received the same volume of drug solvent.