This exploratory study examined breast cancer patients' psychosocial and functional status at the time of diagnosis and during the initial phase of treatment. The purpose was to better understand the impact of diagnosis and treatment on patients' physical state and psychosocial well-being. A convenience sample was drawn from a population of newly diagnosed stage 1 and 2 breast cancer patients undergoing either modified radical mastectomy or lumpectomy with radiation. Subjects completed instruments designed to measure uncertainty, quality of life, functional status, and reaction to diagnosis on two separate occasions: at the time of diagnosis, but before treatment selection and then approximately 8 weeks after surgery. Data obtained from 52 subjects indicated that patients' perceptual uncertainty and various aspects of their functional status declined over the initial course of treatment, but that quality of life was unaffected. The results also showed no relationship between type of breast cancer treatment and patients' uncertainty, quality of life, and functional status. Mastectomy and lumpectomy patients also responded in similar ways to the cancer diagnosis. Both groups experienced the same amount of distress and used conformational coping strategies to similar degrees. Clinical implications are discussed and recommendations are made for future research.