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Demography and population biology aspects of the Moorish tortoise, Testudo graeca graeca were studied in the Pare National d’El Kala, north-eastern Algeria. Density, which was assessed by capture-mark-recapture procedures in a study plot of 30 ha surface, was 3.73 individuals x ha(-1). Adult sex-ratio was nearly equal (1.06:1). Sexual maturity was reached at 7-8 years of age in the males and at 9-11 years in the females. The mean age of tortoises was 13.8 +/- 6.4 years (n = 88). Maximum longevity was over 20 years in both sexes. The females reached larger body size than the males. The growth was rapid during the early years of age in both sexes, and tended to stop completely by the 9-12 years of life in the males and by the 8-10 years in the females. The instantaneous growth of adults which were recaptured in multiple years indicated an average growth rate of 11.34 mm/year in the males, and of 26.30 mm/year in the females. Mortality was estimated at 3.94%. The main mortality cause for the tortoises of this population was the occurrence of fires spreading throughout the study area. These data are of interest because demographic patterns of Testudo graeca seem to vary not only because of their relative genetical variability, but also because of their relative environmental stress.