Manganese is an essential trace element for the development and function of the central nervous system. Alterations in manganese concentrations, whether excessive or deficient, can be accompanied by convulsions. This article represents a systematic review of available quantitative evidence that might clarify this issue. We searched The Cochrane Library, Medline and LILACS databases from January 1966 through June 2006 and reviewed all resulting English and Spanish language publications, as well as those possibly relevant in other languages based on their abstracts. The final selection included for this review comprises all investigations in humans and animals that compared manganese levels in any tissue of a group with spontaneous or induced convulsions (with or without antiepileptic treatment) and a convulsion-free control group. The literature search identified thirteen publications since then relevant to the issue, four of which failed to meet our criteria for inclusion. Of the remaining nine, six were in humans and three in rodents. At present, there is no satisfactory explanation for the relationship between low manganese levels and the presence of convulsions. There is a documented correlation between low blood manganese levels and the presence of convulsions in both humans and animals. The lack of evidence indicating whether this is a cause or an effect of the convulsions clearly justifies more detailed follow-up investigations in humans.