The influence of insulin and 2-deoxy-glucose (D-glucose) on the intracellular protozoan Toxoplasma gondii replication in 3T3-L1 cells was investigated. Insulin and D-glucose had a dose-responsive mitogenic effect on intracellular T. gondii replication and development in 3T3-L1 cells. Insulin concentrations between 102 and 101 mg/ml combination of 4.5g/l D-glucose in DMEM medium gave maximum stimulus to T. gondii replication. The number of tachyzoites increased rapidly, with the growth peaking typically on day 3 or 4 of culture, and then declining quickly. However, insulin, in the absence of D-glucose, had comparably less effect on T. gondii growth than two of their combination. D-glucose concentrations significantly affected the tachyzoite replication and appear to be indispensable for maintaining the host 3T3-L1 cells. 2005 Published by Elsevier Ltd on behalf of International Federation for Cell Biology.