Experiments were done on 33 adults cats. After injection of WGA-HRP (5%, 30-60 nl) into the Bötzinger complex, labelled cells were observed in the lateral parabrachial nucleus and the Kölliker-Fuse nucleus. Injection into control sites failed to label the cells in the above two nuclei. Ninety-one respiratory related neurons recorded from the pneumotaxic center were tested by electrical stimulation of the Bötzinger complex. Thirteen neurons (14.3%, inspiratory 11, phase-spanning 2) could be antidromically activated. Results of the present study showed that neurons in the pneumotaxic center sent axons to the Bötzinger complex concerning respiratory control.