This literature review summarizes current knowledge on the systemic levels of selected markers of inflammation in periodontitis. From the available literature it appears that the total numbers of leukocytes and plasma levels of C-reactive protein (CRP) are consistently higher in periodontitis patients compared with healthy controls. Some systemic markers of inflammation discussed in this review are also regarded as predictive markers for cardiovascular diseases. Therefore changes in these markers in periodontitis may be part of the explanation why periodontitis is associated with cardiovascular diseases and/or cerebrovascular events in epidemiological studies. It is hypothesized that possibly daily episodes of a bacteremia originating from the periodontal lesion are the cause of the changes in systemic markers in periodontitis; the overall size of periodontal lesions in the untreated severe patient may amount to 1500-2000 mm2.