The effects of metronidazole at varying concentrations (10(-7)M - 10(-2)M) on certain cellular immune functions were assessed in vitro. Neutrophil chemotaxis to endotoxin-activated autologous serum, random motility and postphagocytic metabolic activity (hexose monophosphate shunt activity, myeloperoxidase-mediated protein iodination and glycolysis) were unaffected. Likewise, metronidazole had no detectable effects on lymphocyte-active E-rosette formation, mitogen-induced DNA synthesis and mitogen-induced protein synthesis.