Purpose: Hospital readmissions within 30 days of initial discharge occur frequently. In studies of elderly patients receiving Medicare, readmissions have been associated with poor-quality inpatient care, ineffective hospital-to-home transitions, patient characteristics, disease burden, and socioeconomic status. Among adult family medicine patients spanning a wide age range, we hypothesize that previous hospitalizations, length of stay, number of discharge medications, medical comorbidities, and patient demographics are associated with a greater risk of hospital readmission within 30 days.Methods: A retrospective case-control study of 276 family medicine inpatients was conducted to determine the factors associated with 30-day readmission. Bivariate statistics were computed and a multivariate analysis using logistic regression was performed to determine the independent effects of each factor.Results: Patients readmitted within 30 days had more hospitalizations, more emergency department visits, longer hospital stays, more comorbidities, and more discharge medications and were less likely to be married. Multivariate logistic regression found that hospitalization within the previous 12 months (odds ratio, 2.71) and long hospital stays (odds ratio, 2.16) were associated with 30-day readmission; being married (odds ratio, 0.54) had a protective effect.Conclusions: This study demonstrates that factors previously found to be associated with 30-day readmission among elderly patients receiving Medicare also apply to family medicine patients of all ages. It also demonstrates prior hospitalizations, length of stay, and marital status are useful proxies for many more complicated factors, such as disease burden, medical complexity, and social issues, that influence hospital readmission. (J Am Board Fam Med 2013;26:71-77.)