Impedance methods are routinely used to estimate the concentration of viable bacteria in a culture. We have adapted an impedance method to monitor the growth of lymphocytes and used it to monitor lymphocyte proliferation in real time. In this method lymphocytes were cultured in modified micro-well strips with transparent indium-titanium oxide coated electrodes at the bottom. The assay was totally automated and did not involve handling of radioactive chemicals. As the method uses a non destructive method of recording the proliferation, the cells could be used for other studies after the proliferation assay. Due to the real time monitoring of proliferation, results could be obtained within 30 h and additional information such as the rate of proliferation and the limiting rate at time-->0 could also be calculated instantly.