The distribution of several peptides in cutaneous, muscular and visceral primary sensory neurons was investigated in the adult rat. The fluorescent dye Fast blue was applied to the proximal ends of transected saphenous (cutaneous), gastrocnemius (muscular) and greater splanchnic (visceral) nerves. Sections from corresponding dorsal root ganglia were incubated for simultaneous indirect immunocytochemical demonstration of calcitonin gene-related peptide (CGRP)-, substance P (SP)- or somatostatin (SOM)-like immunoreactivity (-LI) and Fast blue. In addition, the presence of fluoride resistant acid phosphatase (FRAP)-enzyme activity (-EA) in retrogradely Fast blue-labeled saphenous and gastrocnemius nerves was investigated by subsequent enzyme cytochemical analysis. The results revealed the presence of CGRP-LI, SP-LI, SOM-LI and FRAP-EA in cell bodies of primary sensory neurons which project to the saphenous and gastrocnemius nerves. CGRP-LI and SP-LI, but not SOM-LI, were found in splanchnic sensory neurons. The vast majority of the visceral sensory neurons were found to contain CGRP-LI.