It was reported that Con A-induced, Luminol-dependent chemiluminescence response of human peripheral lymphocytes might be inhibited by scavengers of reactive oxygen species (ROS), ie, vitamin C, sodium benzoate, mannitol, L-histidine, superoxide dismutase (SOD) and catalase. It was suggested that human lymphocyte chemiluminescence (Ly-CL) is related to the generation of ROS after lymphocytes were stimulated with Con A. ROS participating in human Ly-CL contained ·OH, ¹O₂,H₂O₂, O₂^-_· and so on. The higher the concentraction of Ca²⁺-channel blocker——Verapamil presented, the lower the intensity of human Ly-CL observed. Probably, human Ly-CL depended on increased intracellular [Ca²⁺] of lymphocyte stimulated with antigens or mitogens. These findings propose that human Ly-CL may be an early events of lymphocyte activation.