A simple and rapid method suitable for the analytical evaluation of "Tinctura opii" preparation has been proposed. Optimization of the conditions for capillary zone electrophoresis (CZE) was based mainly on the evaluation of the influence of beta-cyclodextrin (beta-CD) and its synthetic derivatives dimethyl-beta-cyclodextrin and carboxymethyl-beta-cyclodextrin (CM-beta-CD) on the separation of morphine, codeine, thebaine, and papaverine as major alkaloid consitutents of "Tinctura opii". The best separation was achieved using the background electrolyte consisting of 30 mM aspartic acid and 30 mM beta-alanine (pH 3.7) with the addition of 5 mM CM-beta-CD. Experimental results demonstrate a high separation power of CD-modified CZE for the structure related morphine alkaloids. (in Czech)