Abstract: Injectable activated carbon suspensions are proposed for the presurgical marking of nonpalpable mammary pathologies for the purpose of achieving better diagnosis and treatment. These are suspensions that flow freely and without the formation of obstructing aggregates in the needles used during their application, with carbon particles of micron granulometry limited to less than 50&mgr; and preferably between 2&mgr; and 6&mgr; in concentration of approximately 4.0% p/v in saline aqueous medium. A process is also proposed for preparing said compositions.