A microchip-based cell response assay system to an anticancer agent was developed. The hepatoma cell line HepG2 was used to assess the effects of an anticancer agent, doxorubicin. The required cell number was reduced by two orders, and the observation of the time course of cell response became possible. The system clearly showed that treatment with higher doses of the drug or longer exposure times gave more effects to cells. The possibilities of novel drug response studies or toxicity assay system were demonstrated.