To examine a circadian variation of symptom onset of acute myocardial infarction and unstable angina two years register of possible all acute coronary events in a population of Podhale was performed. The time of onset of acute coronary events was determined on the basis of patient self-report. One criterion for exclusion in the study was inability to establish reliable time of onset of acute symptoms. The study group comprised 366 patients aged 61 years, range 29-89 years, men 212, mean age 59, women 154, mean age 64. The distribution of symptom onset within 24 time intervals tested for uniformity by a chi-square test for goodness of fit shows significant (p < 0.01) morning peak between 7:00-9:00 A.M. in whole group and in a subgroup of AMI. No significant evening peak (17:00-18:00 P.M.) was also found in subgroup of AMI.