Mulliken and Glowacki's classification of peripheral blood- and lymph-vessel abnormalities is based on their clinical course and cellular characteristics, and is therefore clear to and readily usable by the practising physician. In order to make the diagnostic process more accessible, the Haemangiomas and Congenital Vascular Malformations Nijmegen working group has developed a system of diagnostic guidelines on the basis of this classification. The anamnesis should be directed at the following six distinguishing characteristics: presence of the anomaly at birth, growth, involution, change in volume, pain and outflow. The physical examination is directed at the following five characteristics: the possibility of emptying or pushing aside the anomaly, changes in volume during engorgement, murmur/'thrill'/pulsation, phleboliths, and hyper- or hypotrophy. If a diagnosis still cannot be made, then additional investigations may be carried out. Duplex scanning is usually sufficient for this purpose, after which the nature and extent of the malformation can be determined with MRI. On the basis of the results, the persons involved can be informed as to the prognosis of the malformation and a plan of treatment can be proposed