The aim of this study was to assess the prevalence of the different periodontal disease indicators used in the C.P.I.T.N. per sextant in the Spaniard population under 20 years of age. We have examined a randomly chosen sample of 1450 school-aged individuals, 7, 12 and 15 to 19 years old. We have observed a healthy periodontium more frequently in the upper anterior region, calculus predominates in the lower incisors close followed by molars, and periodontal pockets of 4 mm or deeper were commonly found in the molar regions. We could'nt detect important deviations from this distribution pattern in the different age groups or between males and females.