Direct biological monitoring is essential for effective assessment efforts. Past approaches to biomonitoring are too simplistic (for example, toxicity testing, indicator species) or conceptually invalid (diversity indexes). Assessments that use ecological guilds use ecological principles in a more integrative fashion. The best long-term approach is development of suites of metrics, like those used in the index of biotic integrity (IBI), to reflect individual, population, community, and ecosystem attributes in an integrative framework. Efforts to use the conceptual content of IBI in a wider diversity of habitats should be encouraged and followed up with effective control actions. (Copyright (c) 1987 Springer Verlag New York, Inc.)