The internal patterning of allelic correlations in the Gainj and Kalam swidden horticulturalists of highland Papua New Guinea is examined within the context of Sewall Wright's F-statistic model. A multiallelic extension of the model is given first, and multivariate variance-component estimators for the parameters are suggested. Then, it is shown that the expectation of the F-statistic set depends on the age structure of the population and that knowledge of the population and sample age structure is critical for meaningful analysis. The array of F-statistics estimated jointly over five polymorphic enzyme loci reveals the following features of Gainj and Kalam population structure: (1) significant departures from panmictic expectations and (2) characteristics of a continuously distributed breeding population, rather than those expected for populations subdivided into demes with discrete boundaries. Finally, the F-statistics estimated for the Gainj and Kalam are briefly compared to estimates obtained from other tribal populations. It is seen that the level of differentiation observed in the Gainj and Kalam is only about one-third that observed in South American swidden horticulturalists. Consequently, some conventional wisdom regarding the interrelationship of socioecological settings and genetic structures may require reevaluation.