Management of marine mammals is often constrained by limited knowledge of reproductive variables and / or age-specific survival rates. I reviewed the use of analyses of tissue samples obtained through biopsy sampling to determine reproductive condition or age of marine mammals, free-ranging cetaceans in particular. Literature searches show that reproductive condition has been successfully determined from blubber biopsies for one species, while no study used such biopsies to determine ages of individuals. I suggest that hormonal assays using muscle or blubber tissue obtained from biopsies could easily be used to determine reproductive condition. However, a study needs to be conducted to define age-related changes in selected hormones if hormonal assays of tissues obtained from biopsies are to be used in marine mammal age determination.