Anecdotal evidence suggests carbamazepine as treatment of impulsiveness in chronic psychotic patients. Several carbamazepine-related side effects have been reported in the literature and, among them, serious cutaneous reactions are the most frequent. Erythematous lesions onset, during the first carbamazepine introduction, suggest an idiosyncrasic nature of this reaction. We report here two clinical cases of two men, respectively 30 and 53 years old, affected by chronic psychosis, showing persecutory and reference delusions, auditory hallucinations and aggressive behaviour. Both were treated with carbamazepine (at a dose of 200 mg/day in the first patient, and of 400 mg/day in the second one), antipsychotics and benzodiazepines. After two weeks of carbamazepine treatment, a cutaneous reaction was shown in both cases: it was a papular and erythematous lesion, mainly spread on hands, feet and shoulders. Therefore, patients complained about pricking, fatigue and headache. Medical and allergological tests (Prick test, Patch test) were performed, but serum IgE levels were not reasonably related to an allergopathy; furthermore cutaneous tests were all negative. Carbamazepine treatment was discontinued and a steroidal i.m. therapy was performed for four days, with a gradual resolution of the symptoms. These two clinical cases suggest that cutaneous reactions carbamazepine-related could represent a serious side effect of this treatment. These reactions, dose and time independent are related to genic abnormalities involving alleles HLA-A31:01 e HLA-B15:02 (Genin et al., 2014). Pharmacogenetic studies to identify predictive factors of individual susceptibility to carbamazepine response are needed.