Twenty-five years ago, George Engel proposed a challenge to the biomedical model and its limited view of disease as biologically rooted. Building on Engel's work, we present the Interactive Biopsychosocial Model (IBM). The IBM argues for a reorientation in biomedicine where research, education, and clinical practice: (1) address health in addition to illness; (2) aim to decipher interrelated biophysical, psychocognitive, and social processes in health and disease, rather than seek a single root cause; and (3) take into account the social networks of the individual to achieve, maintain, and maximize health and well-being for individuals, their significant others, and society. Based on an interdisciplinary collaboration of medical and social scientists, this paper demonstrates the application of the IBM to understanding and generating hypotheses about the longitudinal relationship between sexuality and health, and sexuality and chronic illness (diabetes mellitus) at older ages. The model provides a dynamic, dyadic, framework for building scientific hypotheses about the etiologies and consequences of health, well-being, and disease throughout the life course.