The Oslo Ischemia Study was initiated between 1972 and 1975 in 2,014 men (age, 40-59 years), with the aim of detecting previously unknown and unsuspected coronary heart disease. Of the men who were eligible, 86% participated and were apparently free from cardiovascular disorders. Following a positive symptom-limiting bicycle test, 109 of the men underwent diagnostic coronary angiography and 105 were evaluable; the angiograms were normal in 36 and pathologic in 69. Nineteen of the men with pathologic angiograms had mild angina on the exercise test, while 50 (72%; 2.5% of total study population) remained completely asymptomatic. During a mean follow up of 15 years, 14 of the 50 completely asymptomatic men died (12 suddenly, 1 of whom had angina pectoris for 5 years). Eighteen of the surviving 36 men remained completely asymptomatic and free from signs of coronary artery disease, other than exercise-induced ST-segment depression. One man had ECG signs of a previous myocardial infarction, on the annual follow up; chest pain as a first presenting symptom was observed in a further 17 of 36 survivors. Repeat angiography was performed in 22 men who experienced either chest pain or worsening symptoms following exercise test; of these, 14 underwent coronary bypass surgery and are still alive. The data appear to refute a 'wait-and-see' policy among subjects with asymptomatic cardiac ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)