Although social well-being (SWB) is recognized as an integral component of health, it is rarely included in health-related quality of life (HRQL) instruments. Two SWB dimensions were identified by literature review: social support (SWB-SS) and social function (SWB-SF). As part of a larger project to develop item response theory-derived item banks and computerized adaptive testing, we developed and tested items for the SWB banks. Item ratings of three large (n greater than 600) datasets were conducted by 15 reviewers. Rasch measurement analyses were conducted to initially define item hierarchies. Out of 83 total items, 8 were removed due to model misfit and 8 were removed because of overlapping item content. We then wrote 11 new SWB-SS and 16 new SWB-SF items to fill content gaps, and edited items to improve comprehension and consistency. A total of 94 items (65 SWB-SS, 29 SWB-SF) was administered by computer to 202 cancer patients. Confirmatory factor analyses, Rasch analyses, and evaluations of construct validity were performed. Patients commented favorably on the content of the items and expressed appreciation for attention to this aspect of their HRQL. Using current psychometric standards for unidimensionality, reliability, and content and construct validity, we derived six preliminary item banks for social support (instrumental support, informational support, positive and negative emotional support, positive and negative social companionship) and two for social function (limitations and satisfaction). The empirical construct hierarchy was consistent with clinical observations; e.g., hobbies and leisure activities tended to reflect more limitations, while meeting the needs of family and friends tended to reflect fewer limitations. Optimal care for patients with cancer or other chronic illnesses includes obtaining a complete picture of patients' physical and properly calibrated item banks, it will be possible to precisely and efficiently measure and monitor multiple HRQL dimensions in individual patients, and use their responses to inform care. Qualitative patient feedback and quantitative analyses suggest that it is possible and desirable to include SWB measures in HRQL assessment.psychosocial health status. SWB measures are important since diseases like cancer and their treatment of relationships, parental responsibilities, work abilities and social activities. With