Objective: To determine the cytotoxicity of Aegle marmelos leaf extracts using the brine shrimp test (BST) method for antitumour study. Methods: Test tubes containing different concentrations of leaf extracts were introduced with ten brine shrimp larvae (10 nauplii) and were maintained at room temperature for 24 hours. The numbers of surviving and dead shrimps were counted. Percentage mortality was determined. LC50 was calculated using graph and Finney Method. Results: Among the three leaf extracts tested, aqueous extract showed significant toxicity to brine shrimps in a dose-dependent manner with low LC50 value of 15.28 μg/mL. Conclusion: From the results it can be concluded that the significant lethality of aquoues extract of Aegle marmelos leaves to brine shrimp is indicative of the presence in this plant of a potent cytotoxic component which warrants further investigation.