This paper describes the development, validation, and reliability of a new measure to assess life experiences reported by adults, the Lifetime Experiences Scale (LIFES). This scale is important because no available measure focuses on both positive and negative life experiences and covers childhood, adolescence, and adulthood. LIFES is a self-report measure consisting of two sections: 75 items (organized into eight domains: school, work, health, leisure, life conditions, adverse experiences, achievements, and people and relationships) regarding lived experiences and blank spaces for non-lived (but desired) experiences. The procedures involved in the development of LIFES are described in detail (e.g., construct, generation of items and questions). Moreover, evidence based on test content, response processes, relations to other variables, and different classes of reliability for community samples are presented. Overall, the results suggest that LIFES presented good evidence of validity and reliability and can be a valuable tool for research and clinical purposes. [ABSTRACT FROM AUTHOR]