OBJECTIVES:To compare the prevalence of certain periodontal pathogens in aggressive and chronic periodontitis in 101 Uruguayan patients according to the valid classification at the time the studies were conducted.METHODS: This analysis is based on studies conducted to detect periodontal pathogens in patients with chronic and aggressive periodontitis in Uruguay using conventional and molecular methods. Both studies analyzed the same microorganisms and used the same recovery and analysis techniques. Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia and Fusobacterium nucleatum were studied.RESULTS: A higher prevalence of F. nucleatum, T. forsythia and P. gingivalis was detected in chronic cases, whereas higher rates of F. nucleatum and P. intermedia were observed in aggressive ones. Within the last one, a higher proportion of P. gingivalis and T. forsythia was detected in the generalized cases and A. actinomycetemcomitans in the localized ones. 2 CONCLUSIONS:The patterns detected are in line with those included in the literature for our country.