The clinical importance of posttraumatic stress disorder (PTSD) symptomatology for cancer patients is unclear. The association between the magnitude of cancer-related PTSD symptoms, comorbidity, and functioning is tested. Breast cancer patients (N = 74) were assessed at diagnosis/surgery, followed, and screened for cancer-related PTSD 18 months later. Participants then completed diagnostic interviews and PTSD (n = 12), subsyndromal PTSD (n = 5), and no symptom (n = 47) patient groups were identified. Posttraumatic stress disorder cases were distinguished by having experienced violent traumas and anxiety disorders predating cancer, whereas subsyndromal cases were not. Also, longitudinal data show that PTSD covarys with poorer functioning and lower quality of life among breast cancer survivors. Both PTSD and subsyndromal PTSD were associated with employment absenteeism and the seeking of mental health services.Studies of posttraumatic stress disorder (PTSD) in cancer patients find that diagnostic rates are low (3% to 14%), but symptomatology falling short of the diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV; American Psychiatric Association [APA], 1994)-PTSD that is subsyndromal-may occur in upward of 50% of patients (Gurevich, Devins, & Rodin, 2002). How disabling subsyndromal PTSD may be for any individual is not fully known; however, the few data suggest that it is so. Stein, Walker, Hazen, and Forde (1997) using community survey data found that individuals with subsyndromal PTSD reported employment problems, social disruptions, and difficulties in the home. Similarly, Ciechanowski, Walker, Russo, Newman, and Katon (2004) found in a general survey of women in a health maintenance organization that quality of life was lower among those with subsyndromal PTSD compared to those with no symptoms. Finally, Marshall and colleagues (2001), using data from over 9,000 adults screened for anxiety disorders, reported that the presence of subsyndromal symptoms significantly raised the risk for suicidal ideation.It is not known if similar disruptions occur for cancer survivors. The majority of the available data come not from studies determining patients' syndromal or subsyndromal PTSD diagnoses, but from patient self-reports of traumatic symptoms found to be correlated with poor quality of life and/or impaired physical functioning (e.g., Diemling, Kahana, Bowman, & Schaefer, 2002;Jacobsen et al., 1998; for a review, see Kangas, Henry, & Bryant, 2002 (Gurevich et al., 2002;Kangas et al., 2002), only 8 studies used diagnostic interviews (e.g., SCID; First, Spitzer, Gibbon, & Williams, 1996). Across studies, 0 to 10 patients with PTSD were identified, for a total of 40 PTSD cases in the literature from over 700 patients assessed (Alter et al., 1996;Brewin, Watson, McCarthy, Hyman, & Dayson, 1998;Green et al., 1998;Kangas, Henry, & Bryant, 2005;Mehnert & Koch, 2007;Mundy et al., 2000;Palmer, Kagee, Coyne, & DeMichele, 2004;Pitman et al., 2001). Thus, a study ...