Preclinical pharmacological studies of two acridine derivatives, dihydrochloride N10-oxide 1-nitro-9-/3-dimethylaminopropylamino/-acridine (C-666) and dihydrochloride 1-nitro-9-[(2-dimethylamino)-1-methylethylamino]-acridine (C-829) are reported. Both compounds are characterized by biological activity, poor absorption from the gastrointestinal tract and local irritant action. Quality differences in an effect of both investigated acridine derivatives on the central nervous system were noted. C-666 proved to be deprived of the effect typical of the central component compounds while C-829 demonstrated mostly sedative activity. Clear dissociation in the effect of these both compounds was seen in in vitro experiments on isolated smooth muscle organs. C-666 acted spasmolytically on the motory action of intestine muscles while C-829 acted spastically. Both preparations had clearly hipotensic influence which can be due to the vascular effect and to their affinity with the intramyocardium transmitting system. Neither a distinctive effect on reproductivity of animals nor the teratogenic action were observed in the functional experiments.