Thermoregulatory behavior is well-documented in turtles (reviewed in Hutchison, 1979; Mrosovsky, 1980; Avery, 1982; Meek and Avery, 1988). Adults of aquatic species of turtles have been observed basking above water (i.e., aerial basking sensu Moll and Legler, 1971) on material such as floating vegetation, logs, and rocks, on sandy areas (e.g., beaches, sand bars), or in shallow water where the temperature presumably is elevated. Turtles may engage in this behavior for several reasons, including: (1) promotion of digestion, assimilation, and/or passage of food or wastes; (2) elevation of metabolic rate in order to pursue subsequent activities; (3) removal of ectoparasites; (4) promotion of synthesis of vitamin D; and (5) acceleration of the rate of development of eggs maturing in adult females (reviewed in Auth, 1975; Avery, 1982). Hatchlings and juvenile turtles are known to display thermoregulatory behavior in captivity. Hatchling and juvenile Chelydra serpentina have a distinct selected temperature when provided with either a terrestrial or aquatic thermal gradient (Williamson et al., 1989). Similar behavior has been observed in captive hatchlings of Trachemys scripta (Moll and Legler, 1971). Although hatchlings basked frequently, they showed a marked increase in basking behavior shortly after feeding. Likewise, juvenile Chrysemys picta, Graptemys geographica, G. ouachitensis, G. pseudogeographica, and even Chelydra spend much time exposed on floating wood or other material in the laboratory, commencing shortly after hatching (Janzen, pers. obs.). This basking behavior may allow increased performance (e.g., competition for food) or improve growth rates (e.g., Williamson et al., 1989). Basking by hatchling and juvenile turtles is important to document because of the potential physiological significance and fitness consequences of this behavior. Physiological models of chelonian thermoregulation typically focus on adult animals. Nearly all studies of basking and thermoregulatory behavior in turtles have involved large juveniles or adults. Young turtles, however, experience the thermal environment differently, owing to their small size which allows for more rapid thermal equilibration (Spotila and Gates, 1975). Furthermore, most studies on the interrelationships among egg size, incubation conditions, and embryonic growth do not investigate the ecological consequences of differential post-hatching growth and survivorship (reviewed in Packard and Packard, 1988), although these traits are thought to be strongly influenced by basking behavior. Additionally, the first years of life essentially comprise the period during which turtles are most susceptible to predation. Most individuals live many years once they have passed through the window of vulnerability of body size (reviewed in Wilbur and Morin, 1988). Nonetheless, we are aware of only four reports documenting basking behavior of hatchling turtles in the wild (Moll and Legler, 1971; Waters, 1974; Auth, 1975; Shealy, 1976). In this paper we describe three separate instances of basking behavior by hatchling and small juvenile emydid (Trachemys scripta and Chrysemys picta) and kinosternid (Sternotherus odoratus) turtles under natural conditions. We also report the circumstances and climatic conditions under which these animals were