This report describes a study of the effects of environmental complexity on managers of semipublic organizations, in particular, school principals. Although some previous empirical studies do estimate relationships between principals' management activities and individual elements of schools' immediate organizational contexts, researchers have yet to determine how principals adjust their activities in complex school contexts comprising many different and even conflicting elements. The results of the study show that in nation-specific analyses: (1) variation in principals' instructional management activity associates with variation in local and national stakeholders' influence on curriculum, variation in curricular and administrative centralization, and variation in school environmental complexity; and (2) centralization contextualizes the effect of local environmental complexity on principals' management activity. In cross-national analyses, however, there are few clear associations between principals' management activity and stakeholders' influence, centralization, or environmental complexity. (Contains 7 tables delineating analyses of the data and 34 references.) (Author)