A method of reducing the variability of glycosylation levels between batches of a recombinant protein having a target glycosylation range, and said target glycosylation range having a midpoint, the method comprising: (a) providing a cell suitable for expressing said recombinant protein; (b) determining upper and lower viable cell density levels for a seed culture of said cells (N-1 VCD), determining upper and lower viable cell density levels for a production culture of said cells (N VCD), and determining the midpoint between said N-1 VCD upper and lower levels, and the midpoint between said N VCD upper and lower levels, wherein the upper and lower viable cell density levels are the range, i.e.,values between and including the upper and lower viable cell density levels, of viable cell densities at which recombinant protein having a glycosylation level within the target glycosylation range is obtained; (c) culturing said cells to a viable cell density which is between about 80% and about 120% of the midpoint between said N-1 VCD upper and lower levels, thereby producing a constrained seed culture; and (d) inoculating a culture medium with said constrained seed culture to make a constrained production culture, culturing said constrained production culture to a viable cell density between said N VCD midpoint and lower levels, and then feeding said constrained production culture; wherein steps (c) and (d) yield a first batch of said recombinant protein from said cells, wherein said glycosylation level of said recombinant protein is within said target glycosylation range; (e) repeating steps (c) through (d) to yield at least one subsequent batch of said recombinant protein from said cells, wherein the glycosylation levels of said first and at least one subsequent batch are between about 75% to about 125% of the target glycosylation range midpoint, and/or the coefficient of variation of the glycosylation levels of said recombinant proteins of said first and at least one subsequent batch is 4.5% or less, wherein the coefficient of variation is the standard deviation (σ) divided by the mean value (μ). (a) providing a cell suitable for expressing said recombinant protein; (b) determining upper and lower viable cell density levels for a seed culture of said cells (N-1 VCD), determining upper and lower viable cell density levels for a production culture of said cells (N VCD), and determining the midpoint between said N-1 VCD upper and lower levels, and the midpoint between said N VCD upper and lower levels, wherein the upper and lower viable cell density levels are the range, i.e.,values between and including the upper and lower viable cell density levels, of viable cell densities at which recombinant protein having a glycosylation level within the target glycosylation range is obtained; (c) culturing said cells to a viable cell density which is between about 80% and about 120% of the midpoint between said N-1 VCD upper and lower levels, thereby producing a constrained seed culture; and (d) inoculating a culture medium with said constrained seed culture to make a constrained production culture, culturing said constrained production culture to a viable cell density between said N VCD midpoint and lower levels, and then feeding said constrained production culture; wherein steps (c) and (d) yield a first batch of said recombinant protein from said cells, wherein said glycosylation level of said recombinant protein is within said target glycosylation range; (e) repeating steps (c) through (d) to yield at least one subsequent batch of said recombinant protein from said cells, wherein the glycosylation levels of said first and at least one subsequent batch are between about 75% to about 125% of the target glycosylation range midpoint, and/or the coefficient of variation of the glycosylation levels of said recombinant proteins of said first and at least one subsequent batch is 4.5% or less, wherein the coefficient of variation is the standard deviation (σ) divided by the mean value (μ).