Many fatal or potentially fatal cardio-cerebrovascular diseases present a definite circadian distribution in their onset. In order to verify if episodes of acute cardiogenic pulmonary edema have a significant daily periodicity in their occurrence, a retrospective analysis of 1,204 episodes has been conducted. In all cases, the hour of the day of onset has been identified with certainty; all episodes occurred in hospitalized patients. The rhythmometric circadian inferential statistical analysis by means of the single cosinor method demonstrates that the episodes of acute cardiogenic pulmonary edema present a significant (p < 0.002) circadian distribution, with a peak at 1:00 a.m. (from 10:00 p.m. to 4:00 a.m.). No significant differences (p > 0.05) were found in the circadian distribution regarding sex, age (less or more than 60 years), absence or presence of arterial hypertension and coronary artery disease. Several factors may contribute to this behavior, especially the relationships between several endogenous circadian rhythms, sleep and disease. The knowledge that acute pulmonary edema is a high chronorisk disease could be of interest for the better understanding of its pathophysiology and for a better causative control and prevention.