A reversed-phase high-peformance liquid chromatographic procedrue is described for the determination of the alkaloids in the Chelidonium majus L. For the analysis of tertiary and quaternary alkaloids, replacement of the commonly applied organic amine modifiers with potassium iodied led to a considerable improvemetn in resolution. By using a gradient elution programme more than twenty peaks were resolved and thirteen tertiary and quaternqry alkaloids were identified. © 1991.