Endogenous levels of cytokinins in an anise cell culture were determined by the use of radioimmunoassay and gas chromatography-mass spectrometry in combination with single-ion monitoring, during proembryonal and embryonal development. In both cultures the highest cytokinin levels were correlated with logarithmic growth (embryonal: isopentenyladenosine, 4 ng g(-1) fresh weight [FW]; isopentenyladenine, 1.4 ng g(-1) FW; zeatin, 3.6 ng g(-1) FW; proembryonal: isopentenyladenosine, 58.3 ng g(-1) FW; isopentenyladenine, 7.9 ng g(-1) FW; zeatin 11.1 ng g(-1) FW). The proembryonic culture medium but not the embryonic culture medium contained isopentenyladenosine up to 28 pg ml(-1) during logarithmic growth. No correlation between different embryonic stages and the endogenous cytokinin level was obvious.