Functional cartilaginous constructs for scientific research and eventual tissue repair were cultivated in bioreactors starting from chondrocytes immobilized on polymeric scaffolds. The scaffolds gradually degraded as the cells regenerated tissue matrix consisting of glycosaminoglycan (GAG) and type II collagen. To facilitate data interpretation and optimize cultivation conditions, a mathematical model was developed which yields the concentrations of oxygen and GAG as functions of time and position in growing tissue. Calculated GAG concentrations were qualitatively and quantitatively consistent with profiles measured via high-resolution image processing of tissue samples cultured at two different oxygen tensions for various periods of time.