Living alone in mid-life is on the rise in the United Kingdom, especially among men. The delay of family formation, increases in partnership dissolution rates and the rising incidence of childlessness are probably key factors in explaining the rise in living alone in mid-life over time. Demographic, economic and sociological theories have related these changes to the rise in women’s economic independence and to ideational changes, such as individualisation and a stronger emphasis on self-actualisation. Although overlooked in the literature, the growing economic uncertainty facing a group of economically disadvantaged men is likely to be equally important. However, there has been scant attention for changes in the living arrangements of the middle-aged in the literature, reflecting a gap in our knowledge of this specific stage in the life course. The main aims of this study are therefore to examine the trajectories into living alone in mid-life and how these differ by gender and socio-economic status, as well as to develop a typology of those living alone. We first use data from the General Household Survey (GHS) for the years 1984-2009 to describe changes over time in living alone. We then use data from Understanding Society (USoc) to investigate the partnership history, kin availability and socio-economic status of middle-aged (age 35 to 64) men and women living alone. We examine the degree of heterogeneity in the population living alone by making a distinction between never and ever partnered men and women living on their own. In the final part of the analysis, we use Latent Class Analysis to construct a typology of those living alone based on partnership history, socio-economic status, gender and age.