Streptococcus pneumoniae causes lobar pneumonitis but primary peritonitis can occur in cyrrotic adults as well as in children affected by nephrosis and immunopathies. In young females peritonitis can be the consequence of infection localized at genital organs. Pneumococcal sepsis is becoming rare with the antibiotic era but resistance to penicillin is actually frequent and is becoming a problem for elderly. We report a case of a young woman affected by spontaneous primary peritonitis and pneumococcal sepsis. The prevalent symptoms were gastrointestinal: diarrhea and emesis. No infectious foci could be detected on imaging studies and during surgery.