Objective: To characterize the types of loneliness in older adults attending senior citizen groups in the municipality of Medellin (Colombia) and its association with sociodemographic variables. Methods: Cross sectional study performed in people 55 years old and over who attend senior citizen groups in the municipality of Medellin for a total of 1,169 respondents in 2011. The "ESTE" loneliness scale, validated for Colombia, was used as the data collection instrument. Results: Greater family loneliness and adaptation crisis were found in men, and greater marital loneliness in women. People without partners expressed more loneliness; as socioeconomic status and academic level increased, the levels of various types of loneliness decreased; adults living alone had a greater level of loneliness. Conclusions: The variables of age, marital status, education level, socioeconomic status, and number of people with whom they live are associated with loneliness in the elderly. [ABSTRACT FROM AUTHOR]