Molecular connectivity has been applied to the search of new compounds with activity against the protozoanToxoplasma gondii, using a stepwise linear discriminant analysis (SLDA) which is able to classify a compound according its activity either as active or as inactive. Among the selected compounds, andrographolide and dibenzotiophene sulfone stand out, both with IC50values lower than 1 μg/m1, which are comparable to these of drugs such as sulfamethoxazole, pyrimethamine and trimethoprim, with IC50values equal to 1.1, 0.04 and 2.31 μg/ml, respectively. These results confirm the usefulness of our topological approach for the selection and design of new-lead drugs active againstToxoplasma gondii.