Continuing the study of meso-substituted trimethincyanines proposed earlier for the homogeneous fluorescent nucleic acids detection, a series of meso-methyltrimethincyanines with different heterocyclic residues was synthesized. The spectral-luminiscent properties of the dyes obtained in the presence of DNA, RNA and bovine serum albumine (BSA) were studied and compared with unsinstituted analogues. The intrinsic fluorescence of meso-methyl derivatives' is much lower than that of unsubstituted dyes. The fluorescence enhancement upon binding with nucleic acids for meso-substituted dyes is up to 102 times while for the unsubstituted dyes it is only 10.5 times. A methyl group not only decreases the intrinsic fluorescence of the dyes, but its presence leads to more strict fixation of the dye molecule in the nucleic acid complex. As a result, the fluorescence of the meso-methyltrimethincyanines nucleic acids complexes is 3–5-fold higher than the fluorescence intensity of the corresponding unsubstituted dyes in DMF solution and within the nucleic acids complexes. In the presence of large BSA excess the protein dyes show only 1.2–9.6 fold increase of the fluorescence intensity. The most hydrophobic dyes with naphtothiazole residue are inclined to interact unspecifically with other biomolecules and their fluorescence enhancement in the BSA presence is 2.2–114 times.