The cockles Cerastoderma glaucum and Papyridea papyracea are found among the most abundant molluscs in Lake Timsah, Suez Canal. Age determination based on shell-ring count was conducted to establish growth curves for their life-span. For this purpose, monthly collections of the specimens were carried out in the period between June 1996 and June 1998. Age composition proved the dominance of two and three years old individuals for both species. In C. glaucum, the shell length varied between 9.9 and 35 mm for males, and between 13.3 and 35 mm for females with a mean asymptotic length of 42.37 and 35.02 mm, respectively. On the other hand, P. papyracea revealed a wide range of shell length that varied between 7 and 60 mm, and had an asymptotic length of 69.51 mm. Some environmental factors that expected to affect growth are also discussed.