Water-soluble azo, phthalein, sulphonphthalein and anthraquinone indicators and reagents were subjected to low-voltage electrophoresis on cellulose acetate sheets at pH 2–12. All dyes except low-sulphonated azo dyes yielded one or more sharp bands showing good mobility and resolution over some range of pH values. The performance exceeded that of other possible planar electrophoresis media. The addition of copper, lanthanum, cetyltrimethylammonium or lauryl sulphate ions caused a marked and often beneficial change in behaviour.