RESUMEN
Loneliness is a prevalent set of negative feelings associated with unsatisfactory and reduced social interactions, inadequate social support, poor satisfaction with life and health, negative emotions, and economic burden. Thus, its measurement is of foremost importance. Therefore, this study aimed (i) to devise the Portuguese version of the three-Item Loneliness Scale (T-ILS), which is ideal for epidemiological studies, and (ii) to evaluate its psychometric properties. Three hundred forty-five community-dwelling Portuguese adults with a mean age of 54.6 ± 19.5 years, 61.7% women, recruited door-to-door, were assessed with the Portuguese versions of T-ILS, Satisfaction With Life Scale-SWLS, Lubben Social Network Scale 6-items-LSNS-6, a question regarding Happiness/Unhappiness, and a sociodemographic questionnaire. The T-ILS showed good psychometric properties and correlated moderately with SWLS and LSNS-6, and happiness, and weakly with the number of people in the household. The Portuguese version of the T-ILS proved to be a valid and reliable instrument, easy and quick to administer. It proved to be a valuable tool in screening loneliness in Portugal, being potentially useful to the identification of lonelier people in need of intervention.