The composition of rear-fanged colubrid snake venoms is largely unknown due primarily to the difficulty involved in venom collection. Several different methods have been used to maximize the yield of Duvernoy's secretions. The method proposed by Rosenberg in 1992, which includes the use of ketamine hydrochloride anesthetic and pilocarpine to induce Duvernoy's glands secretion, was used in the present study to collect venom from eight species of colubrids. Protein concentrations, using a dye-binding microassay technique, were determined for the venoms collected. Average protein concentrations ranged from 49.8 to 96.4%. Most yields (dry weight/snake) obtained from specimens in this study were significantly greater than yields previously reported. There was a wide range of effects that occurred due to the ketamine injections; however, all snakes recovered from the effects of the ketamine hydrochloride/pilocarpine with no apparent ill effects. Recommended doses of ketamine hydrochloride have thus been adjusted, depending on previous reactions to the drug. The use of ketamine/pilocarpine in the collection of Duvernoy's secretion has proven to be highly effective in increasing yields. Some caution should be observed when administering ketamine to various species of colubrids, as effects do not necessarily scale to body mass.