This is the longest Asian pitviper, adults are usually 30 to 80 cm long. Body usually pale greenish-brown, or yellowish-olive (sometimes pale brown), w/ alternating, darker brownish or greenish dorsal blotches, each bordered w/ yellowish scales. Head large, triangular, distinct from neck, narrow dark postocular stripe.
Scalation includes 23 or 21 rows of dorsal scales at midbody, 125-135 ventral scales, 36-55 paired subcaudal scales and 8 (sometimes 7 or 9) supralabial scales.
The color pattern consists of a gray ground color overlaid with a series of dark gray of grayish-black crossbands. A ventrolateral pattern of black spots against a gray-white background is also present.
