Klippel-Trenaunay-Weber syndrome (KTW) is a rare phacomatosis whose main characteristics are: cutaneous angiomas (vascular nevi), varicose veins (arteriovenous fistulae) and hemihypertrophy of bones and soft tissues. This is a case report of KTW syndrome which was diagnosed in the first days of life on the basis of characteristic vascular nevi on the skin of the trunk and extremities in addition to hypertrophy of the left part of the body. Neuroradiologically verified hemimegalencephaly associated with temporal hemangioma represents a special particularity in our case. Measures of monitoring the child as well as stimulating and therapeutic actions were the issues of discussion.