A group of 39 males divided into three groups according to age and with no clinical or instrumental signs of cardiovascular disease was studied by continuous 24‐h electrocardiogram recording. All the subjects were under the same sleep‐wakefulness cycle and meals schedule. Single cosinor analysis demonstrated significant circadian rhythms in heart rate for all the subjects. Multiple regression analysis revealed the existence of a significant inverse relationship between age and mesor and amplitude of the rhythm. Analysis of variance and extended Tukey test demonstrated significantly different mesors and amplitudes among the three different groups of ages. We conclude that aging is characterized by a progressive decrease in mesor and amplitude of the circadian rhythm in heart rate.