Postmastectomy lymphedema of the upper limb is usually managed conservatively. Patients are often advised to use elastic bandages or sleeves during the day: elastic compression is, in fact, generally considered the mainstay of lymphedema therapy by authors who advocate the addition of cyclical instrumental or physical treatments, such as pneumatic compression or manual lymphatic drainage. The results of elastic compression, however, have never been extensively analyzed. In the present study, we describe the patterns of response during six months of use of a standard elastic sleeve in a series of 120 patients with postmastectomy lymphedema. Univariate and multivariate analyses were performed to identify possible prognostic factors for a better or worse response. Overall, limb measurements were reduced by 14.7 percent, with weight gain after surgical treatment resulting as the only significant independent negative factor: patients who did not increase weight after mastectomy achieved nearly a 25 percent reduction of lymphedema. These results should be considered during the selection of patients for protocols of lymphedema treatment and the analysis of results.