Newborns present a certain degree of immunological immaturity, which makes them highly susceptible to infection. As interleukin-2 (IL-2) is a cytokine that increases the immune response, we performed this study with the object of determining whether there are differences in the serum levels of IL-2 in healthy newborns and those affected by neonatal sepsis in order to establish if there is an increase in the production of IL-2 in systemic neonatal infection. We studied three groups of newborns: group 1-20 healthy full-term newborns; group 2-19 healthy preterm newborns; and group 3-11 infected newborns. The study was performed before the seventh day of life. IL-2 levels were determined by radioimmunoassay (RIA). Covariant analysis showed no significant differences in IL-2 values between the healthy groups (1 + 2) and the infected group (3) (p = 0.7814).