The major nesting areas for loggerhead turtles in Brazil are estimated to produce about 90% female hatchlings on account of their warm temperatures. In the present study, sand temperatures were monitored at the southern cooler end of the nesting range (Comboios, Espiríto Santo): the temperatures were cool enough to produce a far greater proportion of males than at the major beaches further north. Particular beaches may be thermally suited for the production of a particular sex. Protection of rookeries that appear minor in terms of numbers of turtles nesting could be important for the health of a larger population by insuring that there is an appropriate sex ratio. Temperatures were also monitored in a central guarded hatchery, set back from high seas. The hatchery was thermally similar to zones on the beach where turtles commonly lay, indicating that this conservation practice is unlikely to introduce any large distortions of sex ratio on this beach.