Local anesthetics (lidocaine, mepivacaine or bupivacaine) were given as an intravenous infusion to 18 volunteers to study the influence of these drugs on resting ventilation (breathing air) and stimulated ventilation (hypercarbia- or hypoxemia-induced). Control measurements were made of resting ventilation and stimulated ventilation prior to the infusion. The ventilatory measurements were repeated during the latter half of the infusion, when plasma concentrations of these agents were considered to be near steady-state levels (mean plasma levels of lidocaine, mepivacaine and bupivacaine, 3.1 micrograms/ml, 2.7 micrograms/ml and 1.5 micrograms/ml, respectively) and within a range normally achieved clinically. None of the drugs tested affected resting ventilation or ventilation stimulated by hypercarbia. The drugs tested exerted a slight stimulatory effect on ventilation during hypoxemia.