Mannich bases obtained by aminoalkylation of 3H-pyrrolo[3,2-f]quinoline were designed and prepared as potential vasorelaxing agents. Compounds Ia-Va were characterised by IR, 1H-NMR, mass spectral data and elemental analysis; IIb,c-Vb,c were also confirmed by 1H-NMR spectra of reaction mixtures. To estimate their vascular activity, prototypes 1-(N,N-dimethylaminomethyl)- (Ia) and 1-(4-phenyl-piperazin-1-ylmethyl)- (IVa) 3H-pyrrolo[3,2-f]quinoline derivatives were studied in rat-tail arteries. In tissues precontracted with 0.5 microM 5-hydroxytryptamine (5-HT), 3 microM phenylephrine or 80 mM KCl, Ia and IVa showed endothelium-independent relaxing action. In a preliminary study on the cellular mechanisms of Ia, the influence of propranolol, a beta-receptor antagonist, and ketanserin, a 5-HT(2A)-receptor antagonist, was checked. In the presence of phenylephrine, the vasorelaxing effect of Ia was not affected by these inhibitors.