Mycoplasma hominis was isolated from the surgical wounds of two patients. One of these patients developed a septicaemia-like illness after coronary artery vein-graft surgery. Mycopl. hominis was isolated from the sternotomy wound and pleural fluid of this patient but not from his blood. No other pathogens were isolated. The second patient developed a low-grade soft-tissue infection due to Mycopl. hominis in a craniotomy wound; his condition responded to tetracycline treatment. The source of infection in both cases presumably was mycoplasmaemia which was secondary to urethral catheterization. Infections due to Mycopl. hominis are overlooked easily unless appropriate steps are taken to isolate and to identify these organisms.