Previous studies have not addressed regional differences in adaptive arteriolar growth in the surviving left ventricular (LV) myocardium following infarction in appropriately aged animals, namely middle-aged or older. Accordingly, we examined the adaptive post-infarction growth of arterioles in two distinct regions, i.e. the LV free wall (LVFW) and septum, of middle-aged rats. We induced a myocardial infarction (MI) in 12-month-old rats to analyze (1) protein expression in VEGF/Flt-1/Flk-1 and Ang-1/Ang-2/Tie-2 systems, (2) the arteriolar DNA synthesis, (3) the extent of the arteriolar bed, and (4) the alteration in minimal coronary vascular resistance. In both regions, arteriolar DNA synthesis was activated between days 4 and 7 after MI. While, in LVFW, the degree of DNA synthesis declined between days 11 and 14 post-MI, it continued to rise in the septum, and at day 14, the percent of the arterioles undergoing DNA synthesis was comparable in the LVFW and the septum (9.7±1.6 and 7±2.1, respectively). Arteriolar DNA synthesis was mainly associated with up-regulation of Ang-2 and Tie-2 in both LV regions. Although 4 weeks after MI, the arteriolar beds in the LVFW and the septum expanded to the size of sham rats, this growth did not compensate for the greater minimal coronary vascular resistance in the former. Thus, our findings suggest that (1) the dynamics in adaptive arteriolar growth were similar between the two regions, despite a delay in the septum, and (2) the perfusion deficit in post-MI rats cannot be accounted for by inadequate adaptive growth of arterioles.