Assessments of nursery area function were carried out over a 10-year period in a 3-ha oligohaline marsh and creek system ('Project Area 2') and four natural 'control' creeks (Drinkwater, Jacks, Jacobs, and Tooley) located in the Pamlico River estuary, North Carolina. Habitat function was assessed by comparing (1) growth and survival of fish; (2) long-term monitoring of water quality, sediment organic carbon, and the benthic infaunal community; and (3) measurement of benthic food availability. Growth (weight gain) and survival of the fish Leiostomus xanthurus held within enclosures were similar in both created and natural habitats. Species composition, total fauna density, and species richness of the infaunal community of the Project Area and the natural creeks were comparable within 3 years after construction of the Project Area. However, the sediments of the Project Area lacked the woody detrital cover, high peat content, and predominance of silt and clay characteristic of the natural creek sediments. There was no evidence of significant accretion of total organic carbon in the Project Area during the course of the study. This study has heuristically inspired four recommendations concerning assessment criteria of mitigation success. (1) Direct experimentation is needed to assess habitat function for motile species such as fish. (2) Studies of community structure need to be carried out long enough to permit testing of community stability, especially when working in areas exposed to stochastic abiotic and biotic stressors. (3) Measurements of nutritional content of the sediments should include estimates of overall organic quantity and nutritional quality. (4) Site design or restoration techniques should be included in the experimental design of each mitigation effort. Specifically, the lack of replication in these aspects of the mitigation process limits the inferential potential of the study, constrains the ability to make accurate predictions about the probability of success of future mitigation endeavors, and impedes our understanding of the critical mechanisms governing successful habitat creation, restoration, and enhancement.