Biochemistry panels are used to help identify tissue injury (e.g., because of inflammation, trauma or hypoxia) in human and veterinary medicine in part, by detecting increased enzyme activity in serum or plasma after release from damaged tissues. To determine if a similar approach can be used in Homarus americanus, activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), glutamate dehydrogenase (GD), sorbitol dehydrogenase (SDH), amylase (AMY) and lipase (LIP) were measured in tissue homogenates of heart, hepatopancreas, abdominal muscle, proximal intestine, antennal gland, hemocyte lysate supernatant and hemolymph plasma and serum. Activities of ALT and AST were significantly higher in serum than plasma, which was attributed to release of enzymes from hemocytes during coagulation. Reference intervals calculated for plasma enzyme activity at ambient holding temperatures of 2°C to 4°C and 15°C were quite similar. Plasma enzyme activity was not a sensitive test for detecting infection with Aerococcus viridans (gaffkemia) during an experimental trial.