While serotonin has been shown to play an important role in peripheral pain mechanisms, the specific subtypes of receptors involved and their differential distribution between the sensory and sympathetic nervous system remains poorly understood. In this study, the presence of messenger RNA for rat serotonin receptor subtypes in peripheral sensory and sympathetic ganglia was detected using the method of polymerase chain reaction. Lumbar dorsal root ganglia, superior cervical sympathetic ganglia and lumbar sympathetic ganglia were excised from anesthetized Sprague-Dawley rats. Oligonucleotide primers were chosen based on unique regions of complementary DNA sequence for each of the 12 cloned rat serotonin receptor subtypes (i.e. 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1F, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT3, 5-HT5A, 5-HT5B, 5-HT6 and 5-HT7) and high stringency conditions were used during polymerase chain reaction. Within lumbar dorsal root ganglia, the presence of the 5-HT1B, 5-HT1D, 5-HT2A, 5-HT2C, 5-HT3 and 5-HT7 receptor subtype messenger RNAs was detected. Within superior cervical ganglia, the presence of messenger RNA for 5-HT1A, 5-HT1B, 5-HT1D, 5-HT2A, 5-HT3, 5-HT6, and 5-HT7 receptor subtypes was detected. Lumbar sympathetic ganglia displayed banding identical to the superior cervical ganglia with the exception of the 5-HT6 receptor which was not detected in the lumbar sympathetic ganglia. The polymerase chain reaction product from each positively-detected receptor subtype was subcloned and sequenced and found to correspond to published complementary DNA sequences. Findings from this study may direct further efforts to determine the role of 5-hydroxytryptamine receptors in the peripheral nervous system.