Platelet function, estimated from plasma beta-thromboglobulin (beta-TG, ng/ml), is frequently altered in insulin-dependent diabetics (IDDs). As several factors may affect beta-TG, we studied respectively in 15 IDDs, the roles played by: (i) diabetic control evaluated from glycosylated haemoglobin (HbA1); (ii) plasma C-peptide and pancreatic glucagon; (iii) plasma lipids and the relative percentages of fatty acids in total plasma lipids. Plasma beta-TG did not correlate significantly with the first 3 parameters. However, beta-TG was correlated: (i) positively with plasma triglycerides (P less than 0.01), cholesterol (P less than 0.02), phospholipids (P less than 0.05) and total plasma lipids (P less than 0.01) and the percentage of oleic acid (C18 : 1 omega 9) in plasma lipids (P less than 0.01); (ii) negatively with the percentage of linoleic acid (C18 : 2 omega 6) in plasma lipids (P less than 0.02). No correlation was found between beta-TG and the percentages of the other saturated (C16 : 0, C18 : 0), monounsaturated (C16 : 1 omega 7) and polyunsaturated fatty acids (C18 : 3 omega 6, C20 : 3 omega 6 and C20 : 4 omega 6). The present results indicate that beta-TG in IDDs can be markedly improved by all dietary and therapeutic measures which lower plasma lipids and increase the percentage of the linoleic acid in the body.