Abstract
The numbers of serologically verified M. pneumoniae infections [human] in Finland (as a whole and by regions) and in Scandinavia in 1970-1977 were analyzed based on reports collected in the countries concerned. Two peaks of occurrence extended over most parts of Finland and across Scandinavia; there were also separate local epidemics. M. pneumoniae infections showed a periodicity of occurrence but not a regular cyclic pattern. The figures do not necessarily reflect the true incidence of M. pneumoniae infections in the areas investigated.