The purpose of this work was to examine in an open, randomized parallel-group study whether an intervention programme directed towards hypercholesterolaemia, smoking and diabetes mellitus in treated hypertensive men was associated with less complex formation between low-density lipoprotein (LDL) and human arterial proteoglycans than was the case with usual care. The intervention consisted mainly of non-pharmacological treatment, but drug therapy could be instituted to achieve the treatment goals in the intervention group. The intervention programme was associated with a significant reduction in body mass index, and 46% of the patients were on lipid-lowering medication at the follow-up examination. The net differences were (intervention--usual care): change in serum LDL-cholesterol, -0.48 mmol L-1 (95% confidence interval -0.84 to -0.11 mmol L-1), precipitated LDL-cholesterol, -5.5 micrograms (95% CI -9.0 to -1.1 micrograms). The latter remained after adjustment for the difference in serum LDL-cholesterol between groups. Our conclusion is that the multifactorial risk factor treatment programme was associated with a reduced tendency of LDL to form complexes with human arterial proteoglycans.