This study compared concentrations of total protein, lysozyme, and immunoglobulins (IgA, IgG, IgM) in samples of colostrum (n = 101) obtained from mothers of infants < 32 weeks, 32 to 36⁶ 7 weeks, and ≥ 37 weeks gestational age, both before and after pasteurization. Total protein was measured by refraction index, lysozyme by the lysoplate method, and immunoglobulins through the radial immunodiffusion technique. The total protein concentration was greater in colostrum of the < 32 weeks and 32 to 36⁶ 7 weeks categories compared to full-term (P < .001), while concentrations of lysozyme and IgM were similar. IgA concentrations were higher in the < 32 weeks group compared to the full-term and similar to the 32 to 36⁶ 7 weeks group (P < .05). The IgG was higher in the < 32 weeks category compared to 32 to 36⁶ 7 weeks, and both were similar to the full-term (P < .05). Pasteurization significantly decreased all of the factors analyzed.