Conjugated dienes present in the fatty acyl chains of cholesterol esters and triglycerides associated with plasma apolipoprotein B containing lipoproteins of normal and Type 2 (non-insulin-dependent) diabetic patients (n = 17) have been analysed using second derivative electronic absorption spectroscopy. Characteristic spectral patterns for both normal subjects and Type 2 diabetic patients were observed. Cis, trans and trans, trans conjugated dienes in cholesterol esters of lipoprotein B of Type 2 patients and normal subjects were found to be 41.74 +/- 0.51 mg/litre, 8.20 +/- 0.20 mg/litre (p less than 0.01) and 24.70 +/- 0.33 mg/litre, 9.22 +/- 0.06 mg/litre (p less than 0.01), respectively. Levels of these dienes in triglyceride fraction were 21.21 +/- 0.52 mg/litre, 7.72 +/- 0.02 mg/litre (p greater than 0.05) and 15.49 +/- 0.36 mg/litre, 7.91 +/- 0.11 mg/litre (p greater than 0.05), respectively.