This double-blind randomized placebo-controlled study was designed to evaluate the acute effects of orally administered slow-release isosorbide-5-mononitrate (SR IS-5-MN) in 12 patients with chronic stable angina. After a prestudy screening to assess the reproducibility of exercise response, the patients entered the study lasting 5 days. On the first and fourth day of the trial, each patient underwent a bicycle exercise test 4, 8 and 24 hours after acute administration of SR IS-5-MN 50 mg or placebo. Statistic analysis of the results was performed using a 2-way analysis of variance for cross-over design. Compared to placebo, 4 hours after administration, SR IS-5-MN prolonged the exercise time from 525 +/- 162 s to 685 +/- 207 s (p less than 0.05; 30%) and - 1mm time from 437 +/- 147 s to 562 +/- 219 (p less than 0.05; 29%). After 8 hours SR IS-5-MN prolonged the exercise time from 510 +/- 145 s to 615 +/- 189 s (p:ns; 21%), and - 1mm time from 415 +/- 128 s to 522 +/- 205 s (p less than 0.05; 26%). No significant changes were observed 24 hours after SR IS-5-MN administration. The maximal rate-pressure product was significantly increased by SR IS-5-MN 4 hours after administration.(ABSTRACT TRUNCATED AT 250 WORDS)