Recognition of avirulent pathogens by plants activates defense system, cell death and the general broad-spectrum resistance called systemic acquired resistance - SAR. Several components involved in signaling resistance have recently been identified. Resistance gene mediated responses have been classified according to requirement of NDR1 or EDS1 gene. This classification correlates with R-gene structure. Salicylic acid plays central role in SAR. CPR and NPR1 genes function upstream and downstream of salicylic acid, respectively. Recent studies have demonstrated importance of the cell death in SAR. Novel defence signaling pathways that are independent on salicylic acid have been characterized.