A patient undergoing chemotherapy for acute lymphoblastic leukaemia developed bacteraemia caused by Stomatococcus mucilaginosus while he was granulocytopenic. The organism may have been selected from the upper respiratory tract flora during prophylaxis with oral ciprofloxacin and then translocated to the blood stream via the mucosa. The strain produced an API-Staph profile indistinguishable from that of Micrococcus kristinae. Since a catalase-negative reaction is highly suggestive of S. mucilaginosus, the test should be performed routinely if this organism is not to be overlooked.