Glycymeris nummaria is one of three species from family Glycymerididae that lives in the Adriatic Sea. Besides its distribution and abundance, very little information has been published on biology and ecology of this species. The aim of this study was to investigate the age and growth, reproductive cycle and gonadal development, fatty acid composition of digestive gland and adductor muscle tissue and endolith infestation. Sampling was conducted in the Mali Ston Bay in the period from January to December 2010. Results of this study showed that G. nummaria forms annual growth lines from March to June and maximum longevity was estimated at 20 y. According to the von Bertalanffy growth equation values were L∞=71 mm, growth parameter, K=0,11 year-1 and t0=3,736 (r2=0,919). The value of the index growth is 2,74. Glycymeris nummaria is gonochoristic with equal numbers of adult male and female individuals. Spawning was recorded in July and August. Diet is based on detritus during the fall and winter, while phytoplankton and zooplankton were additional food source during the spring and summer. Glycymeris nummaria shows high endolith infection, considering that all the analyzed specimens had macroscopically visible changes of color at the inside of the shell. However, in the majority of individuals (55,38 %) recorded infection is described as level 1 - poor infection. There were no changes to the shell surface area greater than 69,3 %. Determining the distribution of G. nummaria including abundance, biomass and composition of the population was conducted at 7 locations in the Eastern Adriatic. Samples were collected with hydraulic dredge vongolara and SCUBA diving. Glycymeris nummaria was recorded with relatively high biomass and abundance values in Nin bay, while at other sites biomass and abundance values were significantly lower.