Meningococcal infections may develop as episodic or endemic cases particularly among children attending day-care centers, boarding schools or among military personnel. Bivalent (A/C) meningococcal vaccine is applied to all new military stuff since 1993 in Turkey. In this report two cases of meningococcemia and meningitis, developed in two soldiers vaccinated with meningococcal vaccine, were presented. The first case was a 21 years old male patient who was admitted to the emergency service with the complaints of high fever, headache, fatigue and vomiting. He was conscious, cooperative and oriented with normal neurological findings. Maculopapular exanthems were detected at the lower extremities. The patient was hospitalized with the initial diagnosis of sepsis or meningococcemia and empirical treatment was initiated with ceftriaxone and dexamethasone. Cerebrospinal fluid (CSF) examination yielded 10 cells/mm(3) (lymphocytes) with normal CSF biochemical parameters. A few hours later skin rashes spread over the body rapidly, the symptoms got worse, confusion, disorientation and disorientation developed, and the patient died due to cardiac and respiratory arrest at the seventh hour of his admission. The second case was also a 21 years old male patient who was admitted to the hospital with the complaints of fever, headache, painful urination, confusion and agitation. He was initially diagnosed as acute bacterial meningitis due to clinical (stiff neck, positive Kernig and Brudzinsky signs) and CSF (8000 cells/mm(3); 80% polymorphonuclear leukocytes, increased protein and decreased glucose levels) findings. Empirical antibiotic therapy with ceftriaxone was initiated and continued for 14 days. The patient was discharged with complete cure and no complication was detected in his follow-up visit after two months. The first case had an history of vaccination with bivalent (A/C) meningococcal vaccine three months ago and the second case had been vaccinated one month ago. The bacteria isolated from the blood culture of the first case and the CFS culture of the second case, were identified as Neisseria meningitidis by conventional and API NH system (BioMerieux, France). The isolates were serogrouped as W135 by slide agglutination method (Difco, USA), and both were found to be susceptible to penicillin and ceftriaxone. As far as the last decade's literature and these two cases were considered, it might be concluded that N.meningitidis W135 strains which were not included in the current bivalent meningococcal vaccine, gained endemic potential in Turkey. Since N.meningitidis W135 strains may lead to serious diseases, vaccination of the risk population with the conjugate tetravalent meningococcal vaccine (A/C/Y/W135) should be taken into consideration in Turkey.