We evaluated the effects of short-term, high-intensity exercise training and detraining on resting left ventricular diastolic function (LVDF) and maximal aerobic power (VO2max) in 7 sedentary older (age = 68 +/- 4 years) men (n = 5) and women (n = 2). Training consisted of cycling for 60 min with power output set at 70% (Day 1), 80% (Day 2), and 90% (Days 3-5) of the pretraining peak work rate. Detraining consisted of a return to regular exercise habits. LVDF increased 10% in the early (E) flow velocity, decreased 18% in the late (A) flow velocity wave, and decreased 31% in the isovolumic relaxation time. VO2max was increased 12% while plasma volume (PV) increased 10% following training and returned to baseline after detraining. The exercise-induced change in VO2max was directly related to the change in E/A (r = .52) and indirectly related to the change in IVRT (r = -.62). It was concluded that short-term, high-intensity exercise training improves LVDF and is tolerated well in older subjects, and that the calculated changes in PV and aerobic power are similar to those observed previously in a younger population.