Historically, clinicians have suspected that both major and minor stressful events can have health implications. Observations and case reports link severely stressful life events with a sudden onset or worsening of a variety of illnesses. The immune system was quickly implicated as a means to help explain how stressful life events could produce this relationship. The field of psychoneuroimmunology (PNI) is a field of research that deals with the complex interactions between the central nervous system, endocrine and immune systems, and how behavior/stress can modify these interactions. In this review, I have selected some of our papers that represent our efforts to study the effects of stress on the immune response and also include selected papers that describe how our PNI program at The Ohio State University Medical Center has evolved; virtually all of this research has been performed in collaboration with Janice Kiecolt-Glaser and others in our research group.