A retrospective study was performed on the clinical outcome of 23 patients with citrullinemia diagnosed during the last 20 years in our clinic. The study group consisted of 13 patients with the neonatal form of the disease, four patients with the subacute form, five patients with the late-onset form and one with the asymptomatic form. All patients were treated with natural protein restriction, sodium benzoate and arginine administration. Almost all of the neonatal-onset patients were treated with exchange transfusions and/or peritoneal dialysis. Fourteen patients died: 11 with the neonatal form, one with the subacute form, and two with the late-onset form. The general neurological outcome of the patients who were alive was not satisfactory. Despite these results, it was concluded that the prognosis and quality of life of patients with citrullinemia might be improved with early diagnosis and appropriate therapy.