Moraxella (Branhamella) catarrhalis, although commonly isolated from sputum in patients with pneumonia, rarely causes bacteremia. Sodium polyanethol sulfonate is commonly added to routine blood culture media to increase the yield of Gram-negative bacilli. This anticoagulant also inhibits the growth of Neisseria meningitidis. We added strains f Moraxella (Branhamella) catarrhalis to routine blood culture media supplemented with 0.03% SPS. No inhibitory effect could be demonstrated. The rare occurrence of bacteremic Moraxella (Branhamella) catarrhalis pneumonia is not due to an inhibitory effect of routine blood culture media.