Microfluidic devices, such as lab-on-a-chip systems, are highly advantageous for cell engineering and cell based assays. It is a particularly useful approach for development of the in vitro cellular systems mimicking the in vivo environment. In this paper, a novel lab-on-a-chip device for three-dimensional human cell culture and anticancer drug testing is presented. Cells were cultured as Multicellular Tumor Spheroids (MCTS) — the best cancer tumor model developed so far. Diff erent designs were tested and novel technique of microfabrication in poly(dimethylsiloxane) was developed. MCTS were cultured in a system of polymeric microwells, with the network of microfluidic channels for culture medium flow. Design included optimal shear stress and proper nutrients supply for cultured cells. Final design provided MCTS culture for four weeks with the homeostasis-like state achievement, which is characteristic for the in vivo situation