The two tarantula species used in this study were Grammostola rosea, found in Chile, and Haplopelma lividum, found in Africa. As tarantulas become more common in the pet trade, questions about the effects and components of their venom have arisen. Many types of venom are known to contain toxins with pharmacological action. However, the exact mode of action of tarantula venom is unknown. To address the hypothesis that the two tarantula species would have different teratogenicity based on their different evolutionary histories, venom was collected from tarantulas housed in similar conditions. The venom was stored at −20°C until used. A 96-hr frog embryo assay with 20 embryos was performed to determine the LC50 (lethal), EC50 (malformation), and growth effects. Venom concentrations ranged from 0-0.2% (v/v). Mortality, malformation, and length were analyzed using Tox Tools and SYSTAT software. The Grammostola rosea venom had a 96-hr LC50 of 0.101% (v/v) and an EC50 of 0.0963% (v/v). It also resulted in a consistent spinal malformation and reduction of embryo growth. The Haplopelma lividum venom had a 96-hr LC50 of 0.0713% (v/v) and an EC50 >> 0.075% v/v.