A psychometric study has been conducted with the aims of revising the structure of temperament as postulated by the Regulative Theory of Temperament (RTT) and of constructing an inventory which corresponds to the RTT. A starting point for the study was the assumption that temperament refers to formal attributes of behaviour expressed in energetic and temporal characteristics. About 600 items covering 12 characteristics were generated. A study based on linguistic and itemmetric analysis allowed us to reduce the number of items representing the 12 characteristics to a 381-item pool. This set of items served as the basis for distinguishing the temperamental traits and for constructing the inventory: the Formal Characteristics of Behaviour–Temperament Inventory (FCB-TI). A thorough psychometric study and factor analysis of data obtained from over 2000 subjects (both genders, aged from 15 to 80 years) allowed us to distinguish six temperamental traits which have the status of first-order factors. Among them, four–Sensory Sensitivity, Endurance, Emotional Reactivity, and Activity–refer to the energetic aspect of behaviour and two–Briskness and Perseverance–refer to the temporal characteristics. The FCB-TI has satisfactory psychometric characteristics, including Cronbach alpha and stability measures. Studies have shown that the six FCB-TI scales are replica across samples and refer to robust temperament dimensions.