To study the possible role of homocysteine in aneurysmatic progression, in 1994, 112 of 141 male patients with abdominal aortic aneurysm (AAA) diagnosed by population screening were interviewed and examined. Creatinine clearance estimated and total plasma homocysteine (P-tHcy) was measured by gas chromatography-mass spectrometry. Of the 112 cases, 99 were followed with annual ultrasonography and blood pressure measurements for 1–5 years (mean 2.5 years). The mean creatinine clearance was 70.8+/-23.1 ml/min, while the mean P-tHcy was 16.0+/-10.6 mmol/l, significantly increased compared with an age- and sex-matched reference population (P<0.01). however,="" no="" trend="" of="" correlation="" with="" aaa="" size="" or="" aneurysmal="" progression="" was="" found="" concerning="" creatinine="" clearance="" and="" homocysteine="" level.="" there="" were="" still="" no="" trend="" after="" adjustment="" for="" age,="" smoking,="" diastolic="" blood="" pressure,="" and="" initial="" ankle="" blood="" pressure="" index.="" however,="" the="" homocysteine="" level="" was="" positively="" correlated="" with="" decreasing="" creatinine="" clearance="">r=0.36,P<0.01), and="" this="" correlation="" was="" still="" present="" after="" the="" same="" adjustments.="" a="" large="" proportion="" of="" men="" with="" aaa="" have="" mild="" hyperhomocysteinemia;="" this="" does="" not="" influence="" aneurysmal="" progression="" and="" may="" be="" due="" to="" coexisting="" impaired="" renal="" function.="" the="" finding="" might="" explain="" why="" prospective="" and="" intervention="" studies="" cannot="" prove="" for="" certain="" that="" hyperhomocysteinemia="" influences="" atherosclerotic="" progression,="" or="" that="" treatment="" is="">