To investigate the effect of sea tangle on immune function in normal and diabetic states, 10-week old ICR mice were feed control(C) and sea tangle(5) diets containing 5%(w/w) cellulose and 13.6%(w/w) dry sea tangle for 4 weeks. After 4 weeks, three quarters of mice(CD and SD) were made diabetic by intramuscular injection of streptozotocin(150mg/kg bw). On the 4th day after diabetes was apparent by urinary glucose, one third of diabetic mire(CDG and SDG) were treated with glipizide(20mg/kg bw) and the other third(CDM and SDM) with metformin (500mg/kg bw) orally. Spleen weights of diabetic mice with no hypoglycemic drug treatment appeared to be higher in the sea tangle group(SD) than in control(CD), but were not different when drugs were administered. Data on splenocyte proliferation stimulated by lipopolysaccaride from Salmonella abortus equi(0.l$mu extrm{g}$/ml) showed that sea tangle increased mitogen response in normal mice(C group vs S group) and appeared to have the same effect in diabetic mice with or without drug treatment. Splenocyte proliferation induced by concanavalin A(0.1$mu extrm{g}$/ml) also showed similar results, although there were not statistically significant. Concentration of interleukin-2(IL-2) released from splenocytes of the S group seemed higher than from the C group, but the IL-2 concentrations were not different among six diabetic groups. Results of fatty acid compositions of splenocyte phospholipids showed that diabetes reduced arachidonic acid/linoleic acid ratios and that sea tangle intake and glipizide treatments increased contents of polyunsaturated fatty acids. It is concluded that dietary sea tangle has a positive effect on splenocyte proliferation under normal condition and could have the same effect under diabetic conditions. IL-2 appears to be one of factors mediating the effect but involvement of membrane fatty arid changes and other unknown factors needs lurker Investigation. (Korean J Nutrition 31(6) : 973-980, 1998)