Temperament traits are linked to specific patterns in the relationships between neurotransmitters, and similar links were found between neurotransmitters and mental disorders. This talk will discuss contributions of neurophysiological systems regulating consistent aspects of behaviour that emerge both as temperament traits and/or symptoms of mental disorders. The talk will describe neurochemical framework Functional Ensemble of Temperament (FET) that represents a conservative summary of known neurochemical biomarkers associated with universal aspects of behavioural regulation. The FET has an associated with it Structure of Temperament Questionnaire (STQ-77) that is freely available for a fast screening of temperament profiles in 24 languages. The talk will illustrate applicability of the STQ-77 in research and applied psychology.