<p>After axillary lymphadenectomy (ALND) or radiotherapy for breast cancer or malignant melanoma, damage to the lymphatic tissue can reduce the lymphatic transport capacity and increase interstitial fluid accumulation. This can lead to swelling, pain, progressive trophic skin changes and an elevated risk of infections. Moreover, functional impairment of the affected limb can result in significant psychosocial consequences. Affected patients are usually informed about their increased lifetime risk of developing lymphedema and current guidelines from numerous international and national societies recommend that ipsilateral medical interventions, such as vascular punctures for blood sampling or blood pressure measurements should be avoided. If contralateral venous access is difficult, suboptimal puncture sites such as the foot are chosen or a central venous catheter is placed, even though this is associated with limited access and reduced visualization of the puncture site. Unsuccessful venipuncture attempts can cause pain, discomfort and functional limitations; in particular, placing peripheral intravenous catheters at suboptimal sites such as the foot can substantially impair mobility and thus increase the risk of complications such as deep vein thrombosis. Until recently, evidence on ipsilateral procedures was scarce and largely derived from small case studies; however, emerging data indicate that isolated procedures such as venous puncture and catheter placement can be safely performed following ALND or axillary radiotherapy in the absence of pre-existing lymphedema. Likewise, noninvasive methods (e.g., blood pressure measurements) do not appear to elevate the risk of lymphedema, although ipsilateral interventions should remain contraindicated in patients with established lymphedema. Thus, following an unsuccessful contralateral puncture, an ipsilateral puncture should be considered before selecting unfavorable puncture sites or considering the placement of a central venous catheter.</p>