Nearly 30 years ago, Calder and King (1974), noting that metabolic rates on 38 species of passerine and 34 species of nonpasserine birds had been measured since 1950 and recognizing the predictive power of allometric equations, asked whether it was better to add more birds to the list or to ask new questions. Of course, both happened. In fact, adding more species to the list in part led to new questions. Among these developments has been the ability to look at groups of birds in terms of both their phylogeny and their ecology. One such approach has been to single out seabirds as an ecological group (Ellis 1984, Nagy 1987). In the more than 15 years since a comprehensive review of seabird energetics has appeared (Ellis 1984), the information on basal metabolic rates (BMR) in this group has doubled and the reports on field metabolic rates (FMR, using doubly labeled water) have more than tripled. New analyses using both of these measurements have appeared during that time. It is the goal of this chapter to summarize our current knowledge of seabird energetics, provide a comprehensive review of BMR and FMR measurements, and examine many correlates of both. The relationships of BMR with color and activity pattern (Ellis 1984) need no further development. However, unlike the earlier review, we treat thermoregulation and provide information on thermal conductance and lower critical limits of thermoneutrality. For a comprehensive treatment of avian thermoregulation, refer to Dawson and Whittow (2000). Lustick (1984) remains the best source on seabird thermoregulation generally. Ellis (1984) demonstrated a latitudinal gradient for BMR in Charadriiformes. We reevaluate that gradient and consider whether such an analysis can be extended outside that order. We examine a variety of metabolic costs, including locomotion, and survey information on community energetics, critiquing old models and suggesting new ones.