Ya: lima: po beach in French Guiana exhibits the highest concentration ofleatherback (Dermochelys coriacea) nesting in the world. Scientists and volunteers from more than 25 countries have worked within the Kawana marine turtle project for 16 years. Numbering and tagging of leatherbacks has been the main activity ofthis project. Number of nests per year has been estimated for 13 nesting seasons between 1978 and 1995. More than 50 thousand nestings were recorded annually in 1988 and 1992, but only 10 to 15 thousand annually in 1978-86, 1993, and 1995, with intermediate numbers of20 to 30 thousand annually in 1987, 1989, 1991, and 1994. A general increase in the number of nests has been observed in the last few years as compared to the first years, but the actual trend is unclear. Analysis of the database of tagged leatherbacks (over 31,000 data points) elucidates behavior of this species within and between nesting seasons.