The hybridoma cell's maximum capacity for monoclonal antibody (MAb) production is estimated to be 2300–8000 MAb molecules/cell/s, using measured rates of transcription and translation, and the limitations imposed by the size of the polymerase molecule and the ribosome. Nearly all the production rates reported in the literature fall into or below this range of production rates. Data from batch cultures of hybridomas demonstrate a constant specific rate of MAb production until the time integral of the viable cell concentration reaches about 108 cells · h/cm3. At this point, some essential nutrients from the standard media are depleted, causing MAb production to decline.