Background of research: This research has an attempt to establish a correlation between 5-HTTLPR polymorphism and personality traits in view of the fact that earlier researches have already established that medication via serotonin transporters are efficient in the treatment of anxiety and depression disorders. Researches to date have been focused on the correlation between 5-HTTLPR polymorphism and personality traits, but no research has been conducted among Caucasian population concerning the correlation between 5-HTTLPR polymorphism and alexithymia. Aim of the study: The purpose and aims of this work was to conduct research into the frequency of individual 5-HTTLPR allele, the correlation between 5-HTTLPR polymorphism and alexithymia, the correlation between 5-HTTLPR polymorphism and the dimensions of temperament and character evaluated by TCI Questionnaire and correlation between 5-HTTLPR polymorphism and temperament traits evaluated by a TEMPS-A-SV Questionnaire, as well as to explore the correlation between alexithymia and certain temperament traits and specific character. Methodology: The sample included 96 examinees of both sexes, at the age of 18-60 years, physically and mentally healthy individuals (medical and non-medical staff at the Clinical Hospital Centre Sestre Milosrdnice, the General Hospital Zabok, students at the Zagreb University and the employees of the Police Force). Questionnaires which were applied were as follows: TAS-26, TCI and TEMPS-A, SV. Genotypisation of serotonin transporters was conducted through PCR and RFLP methods. Results: In view of the aims, the following allele frequencies were established : 65,1 % l allele and 34,9 % s allele. A positive correlation was found between s allele and a higher degree of alexithymia. A statistically significant difference between genotype l/l was established in the dimension of harm avoidance (HA), between genotype l/l and l/s in self-transcedence (ST), and a positive correlation between s allele and self-transcedence (ST) and cyclothymic temperament. In addition a positive correlation was found between alexithymia and harm avoidance and self-transcedence (ST). A positive correlation was only found for anxiety temperament.