Mycoplasma pneumoniae causes respiratory infections, but in as many as one out of four of those having contracted the infection symptoms may appear elsewhere, sometimes without preceding respiratory symptoms. Among these, symptoms of central nervous system origin are most the common. Specific diagnosis of the infection is demanding, and is mainly based on serology. Application of nucleic acid detection tests might lead to an earlier diagnostics. Efforts associated with diagnosis should mainly be targeted at detecting epidemics as well as diagnosing patients with severe or abnormal symptoms during the epidemy.