In this paper, we present a new questionnaire for the assessment of self-control as an individual trait. We describe the process of construction of this assessment tool. We also report the results of relevant validation studies. The questionnaire has two independent versions, one based on self-reports and another one based on other-reports. The first version consists of five subscales, called Initiative and Persistence, Proactive Control, Switching and Flexibility, Inhibition and Adjournment, and Goal Maintenance. Seven samples of participants took part in (...) the validation study. The second version has not been split into subscales. Both versions obtained satisfactory indices of internal consistency, assessed with Cronbach’s alpha. The NAS-50 and NAS-40 scores were highly correlated with other measures of self-control, including Tangney, Baumeister, and Boone’s self-control scale. They also proved to be entirely independent of general intelligence. In conclusion, both versions can be regarded reliable and valid enough, and therefore suitable for the assessment of trait self-control for research purposes. (shrink)