Interest in the stinging apparatus of the sea nettle (Chrysaora quinquecirrha) has been stimulated recently because of the economic problem produced by this organism. Resort activity is severely curtailed during the summer season when the nettle is prevalent. The nettle's toxic activity is loated in the nematocyst and appears to be membrane-bound (1). The chemical composition of sea nettle nematocyst suspensions was determined in order to obtain data concerning the structure of the organelle and the pathogenesis of the sting. Materials and Methods. Adult stages of Chrysaora quinquecirrha were obtained from the Chesapeake Bay during August and September, 1968. Whole tentacles (WT) and nematocyst suspensions (NS) were prepared as described earlier (1). The following chemical determinations were performed on freeze-dried specimens according to standard techniques: N2 (2), Cl (3), C (4), H (4), S (4), O (4), ash (4), P (5), DNA (6), RNA (7), reducing sugars (8), sialic acid (9), glycerol (10), hexosamine (11), saponifiable fats (12), and cholesterol (13). Preliminary experiments were done to determine the conditions for optimal yield of these substances from the jellyfish tentacles. The most reproducible results in the analysis of reducing sugars and sialic acid were obtained after 30-min hydrolysis in 4 N HCI. Mximum yields of hexosamine were obtained after hydrolysis for 1 hr. Internal standards were utilized during all analytical procedures.