This work would continue toward the goals of defining the microfloras of various periodontal conditions in man, understanding the sources and magnitude of variation in the microfloras, and determining the etiologic agents of periodontal diseases. The specific aims of this period of requested support are to discover: 1) the influence of puberty on the subgingival microflora; 2) if the family unit accounts for significant variation of the microflora, and, if so, 2a) if there is a genetic contribution to variance; and 3) to compare the significance of puberty, family, and genetic sources of variance to variation accompanying differences in periodontal status. The initial study population will be pre-pubertal, male, monozygous (MZ) twin pairs. Three samples of subgingival dental plaque will be obtained from each individual. Comparison within twin pairs to between pairs will address aim 2; sampling will be repeated annually as subjects progress through puberty to address aim 1; if family accounts for significant variance as determined from the first year's samples, aim 2a will be addressed by substituting half of the MZ pairs with dizygous (DZ) twin pairs (and also sampling them through puberty). If the flora within pairs of DZ twins is more variable than it is within MZ pairs, genetic factors can be inferred. Aim 3 is accomplished by comparisons of the similarities of the floras within and between individuals, twin pairs, puberty stage, and periodontal status determined by standard clinical measurements of gingival inflammation, bleeding, and attachment level, and by comparison with existent data bases for other periodontal conditions. Puberty stage will be determined by established anthropometric assessments. Floras are defined by randomly selected colonies characterized to the species or subspecies level using polyacrylamide gel electrophoresis of cellular proteins, 35-65 test media for biochemical reactions, gas-liquid chromatography of end products, and serology. Identification is by direct comparison to type or other reference strains. Statistical analysis will utilize methods previously established for the non-normal distributional characteristics of such bacteriological data. In addition, new statistical approaches will be explored.