Objective: Ivermectin and sulphadiazine were tested individually to determine their in vitro effects on Toxoplasma gondii grown in human epidermoid larynx carcinoma (Hep-2) cell culture. Study Design: In-vitro study. Material and Methods: Toxoplasma growth was quantities by an enzyme immunoassay performed directly on the fixed cultures, using a rabbit anti-T. gondii immunoglobulin G as the first antibody and a phosphatase-labeled anti-rabbit immunoglobulin G as the second antibody. For each drug, regres- sion models were used to quantify the relationship between optical density values and antimicrobial agent concentrations in the cultures. Results: The 50% inhibitory concentrations (IC50) of ivermectin and sulphadiazine were found to be 0.2 μg/mL and 7.3 μg/mL after 48 h of exposure, respectively. None of the concentrations tested for each drugs demonstrated toxicity to Hep-2 cells after 72 h of incubation. Conclusion: These results indicate that ivermectin significantly inhibited replication of the tachyzoites of T. gondii RH strain.