The extraction of endogenous 3',5'-cyclic-AMP, 3',5'-cyclic-GMP, 3',5'-cyclic-CMP, 3',5'-cyclic-UMP, 3',5'-cyclic-IMP and 3',5'-cyclic-deoxyTMP from meristematic and non-meristematic regions of Pisum roots is described. Extracts were subjected to a sequential purification procedure involving adsorption chromatography on alumina, ion-exchange chromatography, and preparative electrophoresis. Purified samples were compared with cyclic nucleotide standards by HPLC and UV absorbance spectrophotometry; further analysis was carried out by fast atom bombardment mass spectrometry and mass-analysed ion kinetic energy spectrometry. 3',5'-Cyclic-AMP, -GMP, -CMP and -UMP were found to be present in Pisum meristematic tissue and 3',5'-cyclic-AMP, -GMP, -CMP, -IMP and -dTMP are present in the non-meristematic regions. Data indicate that there is a significantly higher concentration of cyclic CMP in meristematic tissue relative to that in non-meristematic regions.