Amino acid sequences of nerve growth factors (NGFs), purified from the venoms of Indian cobra (Naja naja) and Thailand cobra (Naja naja siamensis) were determined. The sequence of N. naja NGF differed from that reported previously by Hogue-Angeletti et al. [(1976) Biochemistry 15, 26-34]. The sequence of N. naja siamensis NGF was identical to that of Formosan cobra Naja naja atra NGF, determined previously by Oda et al. [(1989) Biochem. Int. 19, 909-917] and to that deduced from the nucleotide sequence of an NGF cDNA from the venom gland of N. naja siamensis, as reported by Selby et al. [(1987) J. Neurosci. Res., 18, 293-298].