Ropivacaine and bupivacaine affect the in vitro growth of rat fibroblasts and monkey kidney Vero cells with bupivacaine generally showing the stronger effect. Up to 3 mM concentration the two anesthetics affect the expression of genes differently for CD2, CD3 gamma, CD40L, IL-2, IL-2R alpha, IL-2R beta, IL-2R gamma, IL-4, and IL-4R during activation of human lymphocytes, with bupivacaine showing the higher effect. Human platelet aggregation is inhibited by the two anesthetics which also show an antioxidant effect on lipid peroxidation of rat liver microsomes. In both cases bupivacaine seems more active than ropivacaine.