To assess any relation between reactive oxygen species (ROS; FORT unit = U.F.) and C-reactive protein (CRP; mg/dl), these indexes were assayed in this pilot study in 28 infants with a historical risk or clinical signs of infection. Values of ROS ranging between 62-966 U.F., and of CRP between 0.16-69.9 mg/dl (R-2 = 0.5669; p < 0.01) were obtained, showing, for the first time, a relation between CRP and ROS.