Mycoplasma pneumoniae is a well-established pathogen; it is rarely isolated from healthy persons. Mycoplasma hominis and Ureaplasma species, known collectively as the genital mycoplasmal organisms, are generally considered opportunists that cause invasive infections in susceptible populations. The 2 Ureaplasma biovars, Ureaplasma urealyticum and Ureaplasma parvum, are now designated as separate species. Separation of these species is not possible except via molecular techniques such as polymerase chain reaction (PCR).