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The benzimidazole moiety is present in a great variety of pharmaceutical compounds with anthelmintic action and other applications. These compounds exhibit native fluorescence which often depends on the substituents on the benzimidazole ring and the solvents. The fluorescence emission also changes with pH. In this article the solvatochromic effect is described in different solvents (polar protic and aprotic, alkanes, pyridine and acetic acid) of a series of new benzimidazole derivatives, namely 1-methyl-6-nitro-benzimidazole (6-NBI), 1-methyl-6-aminobenzimidazole (6-ABI) and 1-methyl-6-(p-tolylamino)benzimidazole (6-TABI). The fluorescence intensity is weaker for 6-NBI than for the other derivatives in all solvents tested due to quenching of fluorescence emission by the nitro group. The excitation and emission wavelengths are red shifted for 6-TABI with respect to those observed for 6-NBI and 6-ABI, due to …