People with severe mental illness (SMI) are often described as lonely and socially incapable – an inability resulting from the mental illness. The aim of this article is to explore experiences of being alone among persons with SMI. The article is based on interviews with 19 persons diagnosed with psychosis who were interviewed between four and nine times over a period of three years. The findings show that experiences of being alone can be identified by two concepts: aloneness and loneliness. The persons in the study appeared as socially able and active in relation to their social lives. However, a social agent does not operate in a void but in interaction with specific living conditions; the experiences of aloneness and loneliness may be viewed as the result of the interplay between the individual and the social and material environment.