A new breed of swine, the Yucatan microswine, that was derived from repetitive inbreeding of selected, small Yucatan swine, was investigated as an animal model of advanced vascular atherosclerosis. Nineteen animals were fed an atherogenic diet for 9.9 +/- 1.5 (mean +/- SEM) weeks before and 19.9 +/- 1.8 weeks after balloon endothelial denudation of all four iliac arteries. In 18 (94.7%) of the 19 microswine, angiography performed at 33 to 87 weeks of age disclosed some degree of luminal diameter narrowing: six animals (33.3%) had one-vessel, six (33.3%) had two-vessel, four (22.2%) had three-vessel, and two (11.1%) had four-vessel disease. In 38 (50%) of 76 denuded arteries, angiographically apparent luminal diameter narrowing was observed as follows: three arteries (7.9%) were narrowed less than 50%; 10 arteries (26.3%) were narrowed 50% to 75%; seven arteries (18.4%) were narrowed 76% to 99%; and 18 arteries (47.3%) were occluded. Sixty-four arteries were harvested from 16 of the 18 microswine with angiographically apparent luminal narrowing, which yielded 748 histologic sections. Maximum cross-sectional area narrowing from atherosclerotic plaque exceeded 90% in 135 (18%) of the sections examined, while 65 sections (9%) were narrowed 76% to 90%, and 127 sections (17%) were narrowed 51% to 75%. Atherosclerotic plaque in these animals appeared histologically similar to the so-called "complex" lesion that is typical of human atherosclerosis, which consists predominantly of collagen with focal calcific deposits and a minor lipid component. The smaller size and lower weight of these animals, in comparison with full-size farm pigs and "minipigs," facilitated transportation, handling, and instrumentation. These findings establish the Yucatan microswine as a useful, representative, and economical atherosclerotic animal model for the evaluation of novel interventional techniques.