Lymphedema and arm swelling following surgical and/or radiotherapy for breast cancer are major complications experienced by as many as 30% of breast cancer survivors. The impact of this chronic condition, which tends to grow worse without treatment, is multidimensional and may include loss of self esteem, depression, severe mobility limitations, chronic pain and predisposition to serious limb infections. Therapy, in the form of manual lymph drainage, when used as a part of complete decongestive physiotherapy, is useful for some persons to prevent the condition's progression and in some cases to reverse significant lymphedema already present. However, a large obstacle to successful therapeutic outcomes is the presence of lymphedema that has become hardened to form fibrotic tissue. Reduction (softening) of fibrotic regions is a needed first step to reduce limb volume and represents a major challenge. Moreover, we believe that the degree and extent of tissue hardening has detrimental effects on blood flow and tissue oxygenation, which are overriding factors affecting the viability and function of the involved tissues and ultimately, the therapeutic outcomes. To test this new concept we plan to investigate the quantitative relationships between local tissue fibrosis, blood flow and oxygenation in arms of postmastectomy women, prior to their lymphedema therapy initiation, and after they complete their course of therapy. The working hypotheses to be tested are: (1) initial tissue blood flow and oxygenation are inversely related to initial fibrosis extent and (2) blood flow and oxygenation changes are directly related to fibrosis improvement with therapy. Measurements will be done noninvasively; skin blood flow by laser-Doppler flowmetry, oxygenation by transcutaneous oxygen tension and fibrosis by assessing arm tissue hardness and recovery properties to a standardized 20 second tissue loading with a calibrated spherical indentor. Study findings are anticipated to provide significant new information relevant to this wide-spread condition.