Abstract: Twenty alkaloids have been studied by thin layer chromatography on non-bound alu- minium oxide plate. With ether-methanol (98:2) as solvent, members of the same alka- loid group, such as Belladonna, Strychnos, Coptis, Opium, and Tea alkaloids were sepa- rated from one another, while Chinchona alkaloids were not. The factors (pH of aluminium oxide and solvents) which influence the separation have been investigated.