Bothrops asper is one of the species of snakes with greater sexual dimorphism. Snakes of both sexes are born with the same size, but between 7 to 12 months of age females begin to grow faster than males. In general, adults measure between 140-180 cm.
The males never reach more than 195 cm in length, while the females have an average size of 185 cm, with a maximum confirmed length of 250 cm.
The females have thick bodies and the largest ones can weigh up to 6 kg, although higher weight specimens have been reported. The head of the females is two or three times larger than that of the males in proportion to their size, and their fangs are also proportionally larger (typically 2.5 cm).