Abstract The non-linear dielectric effect in dilute solutions of some trans -dipyridylethylenes was investigated. A positive non-linear dielectric effect was found for 1-(2-pyridyl)-2-(2-pyridyl)ethylene and 1-(3-pyridyl)-2-(3-pyridyl)-ethylene, and a negative effect for 1-(2-pyridyl)-2-(3-pyridyl)ethylene, 1-(3-pyridyl)-2-(4-pyridyl)ethylene and 4-styrylpyridine. The results indicated simultaneous overall reorientation and internal reorientation of the pyridyl rings about the CC axis. The free energy of internal rotation was calculated based on Piekara's model.