Growth and longevity of Glycymeris nummaria were determined from samples of shells, collected monthly by scuba divers between January 2010 and December 2010 from Mali Ston Bay, eastern Adriatic Sea. Acetate peel replicas of the shell margin (marginal increment analysis) and hinge region of the shell were used to validate an annual periodicity of growth lines and to determine shell age, respectively. Results indicate that G. nummaria forms a narrow growth line after February, when seawater temperatures are at a minimum. Growth lines, visible in the hinge region of all the shells, were used to estimate the age of 76 G. nummaria and provided an estimate of maximum longevity of the species at 20 y. Construction of a von Bertalanffy curve using shell length at age data produced a value of L∞ = 71 mm, a growth parameter (K) of 0.11/y, and time at length 0 was -3.74 y. The growth performance index was 2.74.