We report a case of bacterial CAPD peritonitis in a 57 year old immunosuppressed woman with renal insufficiency caused by a rare species of the Micrococcaceae, Stomatococcus mucilaginosus. This uncommon case shows that the presence of gram-positive cocci in pairs, tetrads and clusters forming whitish-gummy colonies should remind us of the possibility of Stomatococcus mucilaginosus.