The phase of the moon can affect activity patterns of nocturnal animals, and may also affect visibility for motorists. However, surprisingly little is known about whether the risk of a wildlife-vehicle collision (WVC) is associated with lunar phase. We investigated the relationship between frequency of WVC at night and lunar phase for four large ungulate species that account for a high proportion of serious WVC along roads in agricultural and forested landscapes of two continents: wild boar Sus scrofa, roe deer Capreolus capreolus, and red deer Cervus elaphus in Castile and Leon, Spain, and white-tailed deer Odocoileus virginianus in New York State, USA. Three of the four species most frequently collided with vehicles at night during the full moon phase of the lunar cycle; this pattern was evident throughout the year but was stronger during some months. Palabras clave: Collision, Ungulate