Many species of the Neisseria, gram-negative diplococci that are frequ
ent respiratory commensals in humans, have been regarded as being nonp
athogenic or as causing disease in only immunocompromised hosts; in co
ntrast, gram-negative diplococci such as Neisseria meningitidis and Ne
isseria gonorrhoeae are known pathogens. We report a case in which Nei
sseria sicca was the cause of serious infection (with catastrophic con
sequences) in an immunocompetent patient and review the world literatu
re on endocarditis due to N. sicca.