BACKGROUND Collagen and elastin are the basic building stones of the aortal wall. During the process of development of an aneurysm of the abdominal aorta (AAA) degradation and remodelling of elastin and collagen in the intercellular matrix of its wall occurs. The two main types of collagen in the aorta are collagens type I and III. During type I collagen synthesis the carboxyterminal propeptide of procollagen (PICP) is released and during synthesis and degradation of collagen type III the aminoterminal propeptide collagen III (PIIINP). The objective of the present work was to assess to what extent the two factors can be used to follow up metabolic processes in the AAA wal and in plasma in relation to the extent and symptomatology of AAA. RESULTS Samples of venous blood and the AAA wall were examined using radioimmunoanalytical methods. PIIINP levels in venous blood were significantly higher (wall p < 0.01) in patients with AAA (n = 78) as compared with the control group (n = 15). The authors did not reveal a statistically significant difference between the levels of the two factors in the blood of patients with AAA of different extent and symptomatology. The PIIINP concentration in the AAA wal correlated significantly with its extent and symptomatology (wall p < 0.01). CONCLUSIONS Evidence was provided of an enhanced metabolism of collagen type III in the AAA wal with predominant degradation in growing and symptomatic AAA. For complete evaluation of the importance of PICP and PIIINP plasma levels it will be necessary to follow up their dynamics in subjects with growing, small (< 5 cm) AAA.