This article presents a short loneliness scale designed for use in large-scale telephone surveys, addressing the lack of a suitable measure for studying loneliness in older adults. The scale, consisting of three items with simplified response categories, effectively measures overall loneliness. The authors conducted two population-based studies to validate the scale and assess its relationship with objective measures of social isolation. The results show that while there is a significant relationship between objective and subjective social isolation, the association is modest, indicating distinct aspects of social relationships. The study highlights the importance of both dimensions in understanding the aging process and suggests that loneliness is a critical factor in well-being. The scale's reliability and validity are demonstrated through psychometric analyses and comparisons with other measures of social isolation.This article presents a short loneliness scale designed for use in large-scale telephone surveys, addressing the lack of a suitable measure for studying loneliness in older adults. The scale, consisting of three items with simplified response categories, effectively measures overall loneliness. The authors conducted two population-based studies to validate the scale and assess its relationship with objective measures of social isolation. The results show that while there is a significant relationship between objective and subjective social isolation, the association is modest, indicating distinct aspects of social relationships. The study highlights the importance of both dimensions in understanding the aging process and suggests that loneliness is a critical factor in well-being. The scale's reliability and validity are demonstrated through psychometric analyses and comparisons with other measures of social isolation.