Conventionally, diagnostics and phylogenetics of phytoplasmas have been primarily based on the 16S rRNA gene, for which "universal" primers are available that amplify from most phytoplasma 16Sr groups. However, there has been a drive in recent years to develop "universal" primers for other genes that can be used to complement the use of the 16S rRNA gene. This chapter details the use of primers based on the phytoplasma secA gene and describes how these primers can be used in both a single or nested PCR approach for amplification. It also notes the use of appropriate controls that should be undertaken and provides a source for phytoplasma secA sequences that are available in databases that can be used for phylogenetic analyses.