Roads that cross natural areas may exert negative effects on the local fauna. Among them, the most obvious negative effect is vehicular run over. For snakes, the risk of roadkill seems to be higher in habitat generalists, locally abundant or highly mobile species. High snake mortality by roadkill occurs mainly when animals cross roads during terrestrial movements to breeding, wintering, foraging or summering habitats. We here describe snake road mortality at Núcleo Picinguaba, Parque Estadual da Serra do Mar, a protected rainforest area located on the northern coast of the State of São Paulo, Brazil. We sampled a 16 km tract of a paved road from October, 2001 to December, 2002, totalling 5,173 km. We found 60 roadkilled snakes, belonging to 15 species, representing around 58% of the species recorded for the region. More mobile species seemed to be more vulnerable to road mortality than sedentary species. Snake species encountered dead on the road tended to have great mobility, to be active foragers, and to show plasticity in microhabitat use. Road mortality seemed to coincide with age and sex specific seasonal activities. The higher number of juveniles found in May could reflect juvenile recruitment, mainly for more active species and for those with greater dispersion ability. The increased road mortality in October may be a consequence of males searching females during the mating period. Although the density of roadkilled species in the area is poorly known, the relative low rate of snake mortality we found at Núcleo Picinguaba, associated with the small length of the highway inside the park and the relatively low traffic volume, indicate that the actual negative effect of the BR-101 highway on local snake populations is negligible for the most common and abundant species. However, given that the Serra do Mar State Park is a type II park in the IUCN Protected Area Management Categories, measures which result in decrease of snake mortality should be implemented by the park managers.