Sympathetic postganglionic and sensory neurons were labeled by injecting a mixed solution of horseradish peroxidase and wheat germ agglutinin conjugated horseradish peroxidase into the splenic portion or the duodenal portion of the cat pancreas. Labeled postganglionic neurons (about 25,000 cells) were located bilaterally in the celiac and cranial mesenteric ganglia (91%), mainly in celiac ganglia, and in the paravertebral ganglia T5 to L7 (9%), especially in T13 to L2. Labeled sensory neurons (about 2,700 cells) were found bilaterally in the dorsal root ganglia T3 to L5, chiefly in T10 to L1. Some differences were found in the localization of labeled postganglionic and sensory neurons between the two portions of the pancreas. Injection in to the splenic portion revealed more labeled neurons in ganglia on the left side, while injection into the duodenal portion gave rise to a greater number of labeled neurons on the right side. Paravertebral and dorsal root ganglion cells innervating the splenic portion were concentrated in fewer ganglia than those supplying the duodenal portion. Compared to the splenic portion, the duodenal portion tended to be innervated by more cranially located neurons in paravertebral and dorsal root ganglia. These neurons probably control the secretion of the endocrine and exocrine pancreas, but the differences in the localization of the labeled neurons between the two portions may be related to the different intraabdominal positions of the two portions of the pancreas.