The venom of the midget faded rattlesnake has been resolved into eight fractions using anion-exchange chromatography. Fractions 1, 6 and 7 were lethal to mice at protein concentrations equivalent to 3 × ld 50 of the crude venom. Fraction 7 ( ld 50, 0·12 μg/g) contained the major lethal component(s) of the venom. Using disc gel electrophoresis only one major and one minor protein component were present in this fraction. One major and one minor component, both with pI values less than 5, were also observed after isoelectric focusing. One protein band with a pI > 9 was present in Fraction 1 after isoelectric focusing. Injection of this fraction resulted in paralysis of the hind limbs and respiratory distress immediately after injection. Crude venom and each fraction were tested for phosphodiesterase, phospholipase, l-amino acid oxidase, arginine ester hydrolase and phosphomonoesterase activities. Phosphodiesterase activity was detected only in Fraction 1. Phospholipase activities were present in Fractions 6 and 7. l-amino acid oxidase activity was present in Fractions 1 and 2. Arginine ester hydrolase activity was most prominent in Fractions 2–5. Phosphomonoesterase activity was not detectable in crude venom nor in any fraction derived therefrom.