The mechanics of respiration were studied during nitrous-oxide halothane anesthesia in 15 apneic infants (weight range, 2.2-5 kg.) ventilated by a time-cycled constant flow ventilator. The dynamic lung-thorax compliance was 2.8 ± 0.3 ml./cm. of water. The dynamic lung compliance was 3.3 ± 0.3 ml./cm