The lymphocyte subpopulations were investigated in peripheral blood of small-for-gestational age (SGA) and appropriate-for-gestational age (AGA) preterm newborns. In SGA newborns the number and percentage of T lymphocytes were reduced. Among the T lymphocytes, the number and percentage of T helper cells were significantly decreased. The cytotoxic/suppressor T cells were also reduced, but to a lesser extent.