Eleven cationic surface-active agents (aliph. amines, amine oxides, ammonium salts) were synthesized by conversion of resp. amidoamines under lab. conditions and studied for biodegradability (COD, dissolved org. C) and toxicity to Daphnia magna, Straus, in aq. media. The toxicity of metabolites was also detd. The biodegradability depended on the chem. structure of the agents. The decompn. degree was 66.0-98.0% according COD. The highest decrease in COD was obsd. for the Me(2)N(CH(2))(n)CONMe(2) agent, the lowest for the [Me(2)N(CH(2))(15)Me](+)Cl(-) (I) one. The agent contg. the Me(2)N(O)CH(2)(-) showed the lowest toxicity, while the I agent the highest one. The metabolites of the agents did not show any toxicity against the living organisms.