The skin cancer melanoma is one of the most lethal cancers unless detected early; it arises from the uncontrolled growth and spread of pigmented cells in the skin called melanocytes. Scientists are using the new approach of virotherapy to selectively kill melanoma cells while leaving healthy cells alone. One technique for studying melanoma involves combining melanoma cells (dark dots in micrograph below left) with normal skin cells called keratinocytes and collagen to make cancer-bearing artificial skin that can be grown in laboratory culture dishes. One of us (Nettelbeck) and colleagues have devised an adenovirus that can specifically reproduce in melanoma cells. In the center and right micrographs below, healthy keratinocytes appear red; cells infected with the virus show up green. The center micrograph was made using viruses that were not specifically targeted to melanomas. The viruses were able to grow in healthy cells, making those cells look yellow. In contrast, the targeted virus (below right) did not replicate in healthy cells, so none of the cells are yellow.