We present here an innovative experimental methodology for the quantitative investigation of chemotaxis in vitro by live imaging of cell movement in a reconstituted three-dimensional collagen gel. A well-defined chemoattractant gradient is generated by means of a novel direct viewing chamber having two compartments (separated by a membrane), one containing the chemoattractant solution, the other the cell-seeded collagen gel matrix. Cell migration is observed by means of a time-lapse motorized video-microscopy workstation equipped with an incubating system and quantified by image analysis techniques. Experimental results on three different cell lines (Jurkat, fibroblasts, and lymphocytes) are presented for the isotropic control case (no chemoattractant) and in presence of a concentration gradient. Cell motility data are in line with the concentration profile, both theoretically calculated from Fick's law and experimentally measured by epifluorescence microscopy. In particular, a transient peak in cell response was found, possibly due to cell membrane receptor saturation. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 4025-4035, 2013