A crystalline form VI of agomelatine having X-ray powder diffraction diagram and infra-red spectrum as given in the specification, is new. A crystalline form VI of agomelatine of formula (L1) having X-ray powder diffraction diagram and infra-red spectrum as given in the specification, is new. An independent claim is included for preparation of the crystalline form VI of agomelatine (L1). [Image] ACTIVITY : CNS-Gen.; Hypnotic; Tranquilizer; Antidepressant; Cardiovascular-Gen.; Immunomodulator; Muscular-Gen.; Neuroleptic; Anorectic; Analgesic; Anticonvulsant; Antidiabetic; Antimigraine; Cytostatic; Antiparkinsonian; Endocrine-Gen.; Nootropic. No biological data given. MECHANISM OF ACTION : Melatoninergic system receptor agonist; 5-Hydroxytryptamine 2c receptor antagonist. No biological data given.