Early detection and treatment of onset or worsening of breast cancer-related lymphedema (BCRL) can potentially prevent or postpone the condition to progress into a chronic progressive condition or eliminate the risk of infections in the arm (cellulitis). Self-surveillance for BCRL by routinely measuring own arm circumference could potentially enable early detection of onset or worsening of lymphedema. The aim is to determine whether women who have received surgery for breast cancer, can perform self-measures of arm circumference in a reliable and valid manner using written and video supported instructions without in-person teaching by a physiotherapist.